Electrolytic polishing method for preparing single-phase region thermal deformation near-beta type titanium alloy EBSD sample

Abstract

The invention belongs to the technical field of electrolytic polishing, and discloses an electrolytic polishing method for preparing a single-phase region thermal deformation near-beta type titanium alloy EBSD (electron back-scattered diffraction) sample, which comprises the following steps: mechanically grinding a to-be-tested surface of the single-phase region thermal deformation near-beta type titanium alloy EBSD sample, and performing electrolytic polishing after mechanical polishing; wherein the electrolytic polishing solution is prepared in advance and is naturally cooled to room temperature for use; three components of the electrolytic polishing solution and polishing parameters used in cooperation with the components of the electrolytic polishing solution are given, wherein the polishing parameters comprise the polishing voltage, the polishing time, the area, exposed in the electrolytic polishing solution, of the to-be-measured surface of the sample and the flow velocity of the electrolyte. The technical problem that in the prior art, no electrolytic polishing method for the single-phase region thermal deformation near-beta type titanium alloy EBSD sample exists is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic polishing, and more specifically, relates to an electrolytic polishing method for preparing EBSD specimens of a single-phase region thermally deformed near-β type titanium alloy. Background Art

[0002] Near-β type titanium alloys have the characteristics of high strength, high toughness and high hardenability. Their tensile strength ≥ 1200 MPa, or yield strength ≥ 1100 Mpa, and hardness ≥ 370 HB (or HRC ≥ 35). They are the best candidate engineering materials for manufacturing various large load-bearing components in aircraft including large transport aircraft and bombers. Currently, the basic research on the thermal deformation of near-β type titanium alloys mainly focuses on the two-phase region (below the β phase transformation temperature (T β )), while the research on its thermal deformation behavior in the single-phase region (above the β phase transformation temperature (T β )) and various microstructural evolution mechanisms including dynamic recovery, dynamic recrystallization, deformation bands, adiabatic shear bands and microtexture is relatively lacking. Clarifying various microstructural evolution mechanisms of near-β type titanium alloys in the single-phase region and establishing a hot processing map coupled with microstructural evolution mechanisms are of great significance for accurately guiding the β forging (also known as single-phase region forging) of the alloy. Electron Backscatter Diffraction (EBSD) is an advanced characterization technique in the field of materials science and engineering, which combines microstructural and crystallographic analyses to provide an important means for revealing various microstructural evolution mechanisms during the thermal deformation process.

[0003] The accuracy of EBSD analysis is directly proportional to the preparation quality of the surface to be measured of the sample. To obtain a high-resolution EBSD sample, it is necessary to require that the surface to be measured of the sample is smooth, clean, pollution-free, non-oxidized, without a surface stress layer and a phase transformation layer caused by stress contact. If the surface to be measured is locally contaminated or oxidized, false images or orientation maps with low confidence will be obtained; if there is a residual stress layer on the surface to be measured, almost no electron signal will be generated during the diffraction process. All of these factors will lead to the inability to obtain clear and high-quality Kikuchi patterns during the diffraction process, making it difficult to obtain stable, effective and accurate microstructural information. In addition, due to the high strength and hardness of near-β type titanium alloys, EBSD sample preparation is quite difficult, especially for thermal deformation under extreme deformation conditions such as high strain rate and large strain, it is difficult to obtain a high-resolution EBSD sample, thus affecting the accurate characterization of the microstructure. These problems have long troubled scientific research and engineering and technical personnel.

[0004] At present, the main methods for preparing EBSD specimens of low-strength titanium alloys include mechanical polishing, vibratory polishing, and electrolytic polishing. Mechanical polishing involves placing the surface of the sample to be measured after mechanical grinding on a polishing disc with damping cloth and spraying alumina suspension onto the polishing disc simultaneously. This method has a certain effect on low-strength and undeformed titanium alloys. However, for high-strength titanium alloys, especially the near-β type titanium alloys that have undergone large deformation, after a large number of mechanical polishing experiments, it was found during the EBSD process that there was no electronic signal on the surface of the sample to be measured. Therefore, mechanical polishing alone is far from sufficient for high-strength titanium alloys. The mechanical polishing process is time-consuming and has a very low productivity. Since the sample is pressed by a chuck on the polishing disc with a certain force, it is impossible to remove the deep residual stress layer generated during mechanical grinding on and below the surface of the sample to be measured. Moreover, new residual stresses and embedded polishing paste particles will be introduced during the subsequent mechanical polishing process. The embedded polishing paste particles contaminate the surface of the sample and cause various irregularities and scratches on the sample surface. Vibratory polishing achieves a smooth polishing process by generating vibrations close to the horizontal direction without vertical movement, which is not affected by the conductivity of the sample. It effectively reduces sample deformation and edge chamfering, and can reduce the surface stress and roughness of the specimen to a certain extent. However, the vibration amplitude, load, and polishing time of the vibrator have a greater impact on the quality of the surface of the sample to be measured. Usually, more than 24 hours of long-time vibratory polishing is required to largely remove the residual stress layer on and below the surface of the sample to be measured. In addition, due to the high cost of vibratory polishing machines and the fact that they are usually charged according to the polishing duration during daily use, the polishing cost is very high, which is not conducive to large-scale sample preparation for EBSD. The principle of electrolytic polishing is to remove the metal on the surface layer of the sample through the dissolution of the anode metal under the action of electrochemical and mechanical effects. Since the electric field is concentrated at the protruding parts on the surface of the sample (anode), dissolution will occur here first and fastest. Therefore, electrolytic polishing can gradually make the surface of the sample to be measured after mechanical grinding and mechanical polishing tend to be flat and smooth. Since only the anode and cathode that do not come into contact with each other and the electrolyte are in contact during the electrolytic polishing process, no new residual stress will be introduced on the surface of the anode. Therefore, the residual stress layer on and below the surface of the sample to be measured can be completely removed. Compared with mechanical polishing and vibratory polishing equipment, the structure of electrolytic polishing equipment is simple, and the operation process is also very simple. The types of electrolytes, voltage, current density, polishing time, electrolyte temperature, electrolyte flow rate, and exposed area in electrolytic polishing are key technologies that directly determine the success and effect of electrolytic polishing. However, the interaction between the types of electrolytic polishing solutions and other polishing parameters is complex. Currently, there is only an electrolytic polishing method for EBSD specimens of low-strength titanium alloys, and there is no electrolytic polishing method that can be used for EBSD specimens of single-phase region hot-deformed near-β type titanium alloys, which has become a technical problem in this field. Summary of the Invention

[0005] In view of the above defects or improvement requirements of the prior art, the present invention provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy, thereby solving the technical problem in the prior art that there is a lack of an electrolytic polishing method applicable to the EBSD specimen of the single-phase region hot-deformed near-β type titanium alloy.

[0006] To achieve the above object, according to one aspect of the present invention, there is provided an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy, including the following steps:

[0007] After the test surface of the near-β type titanium alloy EBSD specimen hot-deformed in the single-phase region is mechanically ground and mechanically polished, it is subjected to electrolytic polishing in an electrolytic polishing solution that is pre-prepared and naturally cooled to room temperature to obtain a single-phase region hot-deformed near-β type titanium alloy EBSD sample; any one of the following three is adopted for the components of the electrolytic polishing solution and the electrolytic polishing parameters:

[0008] (1) Composition of the electrolytic polishing solution: 3-10 vol.% perchloric acid, 25-50 vol.% n-butanol, and 40-72 vol.% methanol; polishing voltage: 30-50 V, polishing time: 15-50 s, area of the test surface of the specimen exposed in the electrolytic polishing solution: 0.5-1 cm 2 , electrolyte flow rate: 11-13 m / s;

[0009] (2) Composition of the electrolytic polishing solution: 3-10 vol.% perchloric acid, 20-40 vol.% ethylene glycol, and 57-70 vol.% methanol; polishing voltage: 15-30 V, polishing time: 20-45 s, area of the test surface of the specimen exposed in the electrolytic polishing solution: 0.5-1 cm 2 , electrolyte flow rate: 11-13 m / s;

[0010] (3) Composition of the electrolytic polishing solution: 3-10 vol.% perchloric acid and 90-97 vol.% absolute ethanol; polishing voltage: 20-40 V, polishing time: 20-90 s, area of the test surface of the specimen exposed in the electrolytic polishing solution: 0.5-1 cm 2 , electrolyte flow rate: 11-13 m / s.

[0011] Preferably, the near-β type titanium alloy EBSD specimen before the mechanical grinding is an initial specimen formed by cutting the near-β type titanium alloy sample hot-deformed in the single-phase region to have a test surface.

[0012] Preferably, the mechanical grinding is to polish the test surface of the initial specimen successively with 400#, 800#, and 1200# silicon carbide sandpapers.

[0013] Preferably, the polishing liquid used for the mechanical polishing is Al2 O 3 The suspension liquid, and the fabric used for mechanical polishing is damping cloth; after mechanical polishing, it is rinsed with water and then with alcohol in sequence, and after air drying, the above electrolytic polishing is carried out.

[0014] Preferably, the Al 2 O 3 The suspension liquid is a suspension liquid composed of Al 2 O 3 polishing paste with the finest particle size of 0.05 μm and water.

[0015] Preferably, in the first type, the composition of the electrolytic polishing solution: 5-10 vol.% perchloric acid, 35-50 vol.% n-butanol, and 40-60 vol.% methanol; polishing voltage: 35-50 V, polishing time: 20-50 s, the area of the surface to be measured of the sample exposed in the electrolytic polishing solution: 0.5-1 cm 2 , and the flow rate of the electrolyte solution: 12-13 m / s.

[0016] Preferably, in the second type, the composition of the electrolytic polishing solution: 10 vol.% perchloric acid, 20-25 vol.% ethylene glycol, and 65-70 vol.% methanol; polishing voltage: 20-30 V, polishing time: 20-45 s, the area of the surface to be measured of the sample exposed in the electrolytic polishing solution: 0.5-1 cm 2 , and the flow rate of the electrolyte solution: 12-13 m / s.

[0017] Preferably, in the third type, the composition of the electrolytic polishing solution: 8-10 vol.% perchloric acid and 90-92 vol.% absolute ethanol; polishing voltage: 28-40 V, polishing time: 20-45 s, the area of the surface to be measured of the sample exposed in the electrolytic polishing solution: 0.5-1 cm 2 , and the flow rate of the electrolyte solution: 12-13 m / s.

[0018] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the technical solutions provided by the present invention mainly have the following beneficial effects:

[0019] 1. The electrolytic polishing method for preparing EBSD specimens of single-phase region hot-deformed near-β titanium alloy proposed by the present invention involves mechanically grinding and mechanically polishing the surface to be measured of the EBSD specimen of single-phase region hot-deformed near-β titanium alloy, and then performing electrolytic polishing. Three components of electrolytic polishing solution and polishing parameters used in combination with the components of the electrolytic polishing solution are specially designed. The electrolytic polishing parameters are stable, have good reproducibility and high accuracy. Under the components of the electrolytic polishing solution and the electrolytic polishing parameters provided by the present invention, a large number of pre-treated initial samples can be prepared into EBSD specimens that meet the requirements. The prepared EBSD specimens have a high resolution (not less than 86%), extremely high EBSD sample preparation efficiency, low cost and simple method, and are suitable for technicians in universities and enterprises to prepare EBSD specimens of single-phase region hot-deformed near-β titanium alloy.

[0020] 2. The reasons why the polishing parameters for non-high-strength titanium alloys in the prior art cannot be applied to the EBSD specimens of the single-phase region hot-deformed near-β titanium alloy of the present invention are as follows: The electrolytic polishing parameters of the same material in different states and different types of materials are different, resulting in huge differences in the electrolytic polishing parameters of EBSD specimens; and because the higher the strength of the titanium alloy, the greater its hardness value and the worse the electrolytic polishing effect, it is more difficult for EBSD specimens to obtain a high resolution. Especially for titanium alloy materials deformed under extreme deformation conditions of high strain rate and large strain, due to the severe lattice distortion in the titanium alloy after deformation under such extreme conditions, the formation of EBSD Kikuchi patterns is inhibited, so it is even more difficult to improve the EBSD resolution and accurate microstructure characterization cannot be obtained. Therefore, the present invention specially designs three groups of components of electrolytic polishing solution for EBSD specimens of near-β titanium alloy, a high-strength titanium alloy, after hot deformation in the single-phase region and the polishing parameters used in combination with it. The design of the components of the electrolytic polishing solution and the polishing parameters enables electrolytic polishing to be carried out at room temperature.

[0021] In addition, since the electrolytic polishing solution is sensitive to temperature, if the temperature of the electrolytic polishing solution is too high, the viscosity of the electrolytic polishing solution becomes smaller, and the electrochemical reaction becomes more intense, which will cause various defects such as a large number of protrusions, unevenness, corrosion pits, and over-corrosion pits on the polished surface of the specimen to be tested, instead seriously reducing the EBSD resolution and making it difficult to perform accurate microstructure characterization; if the temperature of the electrolytic polishing solution is too low, the rate of the electrochemical reaction slows down, the electrolytic polishing efficiency decreases, and at the same time, due to the increase in the viscosity of the electrolyte, the conductivity decreases, the dissolution of the metal anode is too slow, and the diffusion rate of the dissolved metal ions in the electrolyte slows down, resulting in white cloud-like substances or white spots appearing on the polished surface of the sample after electrolytic polishing, and the overall polished surface becomes dull without showing a mirror-like metallic luster. As a result, the EBSD resolution will also decrease, which will also affect the accurate characterization of the microstructure. This is also an engineering and technical problem that has long troubled scientific research and engineering and technical personnel in the electrolytic polishing sample preparation of EBSD specimens; for the electrolytic polishing solution used for the electrolytic polishing of titanium alloy EBSD specimens in the prior art, such as the electrolytic polishing solution prepared from perchloric acid, methanol, and n-butanol, expensive liquid nitrogen must be added to cool it to -30 °C before electrolytic polishing treatment can be carried out, which increases the complexity of electrolytic polishing and greatly reduces the stability; to solve this problem, the present invention conducts an innovative design of the electrolyte ratio and electrolytic polishing parameters for the electrolytic polishing solutions composed of perchloric acid + n-butanol + methanol, perchloric acid + ethylene glycol + methanol, and perchloric acid + absolute ethanol, so that these three electrolytic polishing solutions do not need to add liquid nitrogen and can be normally used for the electrolytic polishing treatment of EBSD specimens only by natural cooling to room temperature, eliminating the serious impact on the surface quality of EBSD electrolytic polishing specimens and the reduction of the EBSD resolution caused by improper control of the electrolyte temperature, greatly reducing the complexity of the electrolytic polishing method and equipment and reducing the cost.

[0022] 3. When electrolytically polishing a titanium alloy EBSD specimen in the prior art, the current magnitude is usually controlled by immersing the entire specimen containing the surface to be measured into the electrolyte to a certain depth. However, the depth to which the specimen is immersed in the electrolytic polishing solution cannot be precisely controlled. Since all surfaces of the specimen participate in the electrolytic polishing process, the resulting current density is not the current density of the surface to be measured and its value is usually low, making it difficult for the electrochemical reaction to concentrate on the surface to be measured of the EBSD specimen. As a result, the error of the obtained current density is large and the reproducibility is low. In the prior art, since the entire specimen enters the electrolyte, both the surface to be measured and the surfaces other than the surface to be measured of the specimen participate in the electrochemical reaction. This only makes it difficult for the electrochemical reaction to gather on the surface to be measured, prolongs the electrochemical reaction time, and thus greatly reduces the electrolytic polishing quality and efficiency of the surface to be measured. In contrast, the present invention does not require manual control of the depth of the EBSD specimen entering the electrolyte. The current density can be precisely controlled only by specifying the area of the surface to be measured of the EBSD specimen exposed to the electrolytic polishing solution. Except for the exposed surface of the EBSD specimen to be measured, the other surfaces do not come into contact with the electrolyte. Since the EBSD test on the electron microscope is only carried out on a selected area on one surface (referred to as the surface to be measured) of the sample, the present invention can meet the EBSD test requirements by controlling the exposed area in combination with other designed polishing parameters.

[0023] 4. After mechanical grinding of the sample in the prior art, it is necessary to carry out mechanical polishing in a suspension containing harmful health chemicals such as SiO 2 suspension containing hydrogen peroxide. Hydrogen peroxide has strong oxidizing properties and is harmful to health when frequently contacted. The mechanical polishing solution designed by the present invention is a common and safe Al 2 O 3 suspension in the laboratory, which greatly improves the test safety.

[0024] 5. In the pretreatment of titanium alloy EBSD specimens in the prior art, it is necessary to mechanically grind the surface of the sample with silicon carbide sandpaper of more than 3000#. Since the larger the mesh number of the sandpaper, the higher the cost, the present invention only needs to mechanically grind with silicon carbide sandpaper of up to 1200# at most. In comparison, the pretreatment cost of the present invention is lower.

[0025] 6. The electrolytic polishing method for preparing a single-phase region hot-deformed near-β type high-strength titanium alloy EBSD specimen proposed in the embodiment of the present invention first mechanically grinds the surface to be measured of the initial sample with silicon carbide sandpaper of up to 1200# on an automatic grinding and polishing machine, and then immediately uses a suspension of the finest particle size of 0.05μm Al 2 O 3 polishing paste and water for mechanical polishing, which simplifies the pretreatment process of EBSD sample preparation, reduces the pretreatment requirements for the surface to be measured of the EBSD sample, and greatly shortens the pretreatment time of EBSD sample preparation. After the sample pretreatment, it can be electrolytically polished in an electrolytic polishing device to obtain an EBSD sample. Brief Description of the Drawings

[0026] Figure 1 is a flowchart of an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy in an embodiment of the present invention.

[0027] Figure 2 is a macroscopic morphology diagram after electrolytic polishing obtained in Example 1.

[0028] Figure 3 is a macroscopic morphology diagram after electrolytic polishing obtained in Example 2.

[0029] Figure 4 is a macroscopic morphology diagram after electrolytic polishing obtained in Example 3.

[0030] Figure 5 is an EBSD IPF (Inverse Pole Figure) diagram after electrolytic polishing obtained in Example 1.

[0031] Figure 6 is an EBSD IPF diagram after electrolytic polishing obtained in Example 2.

[0032] Figure 7 is an EBSD IPF diagram after electrolytic polishing obtained in Example 3.

[0033] Figure 8 is an EBSD IPF diagram after electrolytic polishing obtained in Example 4.

[0034] Figure 9 is an EBSD IPF diagram after electrolytic polishing obtained in Example 5.

[0035] Figure 10 is an EBSD IPF diagram after electrolytic polishing obtained in Example 6.

[0036] Figure 11 is an EBSD IPF diagram after electrolytic polishing obtained in Example 7.

[0037] Figure 12 is an EBSD IPF diagram after electrolytic polishing obtained in Example 8.

[0038] Figure 13 is an EBSD IPF diagram after electrolytic polishing obtained in Example 9. Detailed Description of the Invention

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Example 1

[0041] As Figure 1 shown, this embodiment provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy, which specifically includes the following steps:

[0042] (1) Sample cutting: Use a wire electrical discharge machine to cut a near-β type TC18 titanium alloy disc sample after single-phase region hot deformation under high strain rate and large deformation conditions along its central axis to form an initial sample with a surface to be measured.

[0043] (2) Pretreatment: Mechanically grind the surface to be measured of the initial sample in step (1) successively with silicon carbide sandpapers of model 400#, 800#, and 1200# on an automatic grinding and polishing machine. After mechanical grinding, mechanical polishing is carried out. The loads used for mechanical grinding and mechanical polishing are the same. The polishing liquid is a suspension composed of an appropriate amount of 0.05μm Al 2 O 3 polishing paste and a certain amount of tap water. The fabric used for polishing is damping cloth. After mechanical polishing, it is rinsed with water and then with alcohol successively, and then dried with a hair dryer at room temperature to obtain a mechanically polished sample.

[0044] (3) Prepare an electrolytic polishing solution composed of 5 vol.% perchloric acid, 35 vol.% n-butanol, and 60 vol.% methanol, and naturally cool the electrolytic polishing solution to room temperature.

[0045] (4) Electrolytic polishing: Pour the electrolytic polishing solution obtained in step (3) into an electrolytic cell. Invert the polished surface of the mechanically polished sample obtained in step (2) on the hole of the selected electrolytic cell cover, and press the voltage conducting head onto the non-polished surface of the specimen; then, set the polishing voltage to 35V, the polishing time to 20s, the exposure area (i.e., the area of the surface to be measured exposed in the electrolytic polishing solution) to 0.5 cm 2 and the electrolyte flow rate to 12 m / s on the control panel of the microcomputer control system, and then save the electrolytic polishing program. Immediately click the start button to start the program for electrolytic polishing treatment; after the electrolytic polishing program is executed, immediately raise the voltage conducting head, take out the specimen and immediately rinse it successively with water and absolute ethanol, and dry it with a hair dryer at room temperature to obtain a titanium alloy electrolytically polished sample with a smooth and flat polished area, as Figure 2 shown.

[0046] Example 2

[0047] This embodiment provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy, which specifically includes the following steps:

[0048] (1) Sample cutting: Use a wire electrical discharge machine to cut a near-β type TC18 titanium alloy disk sample after single-phase region hot deformation under high strain rate and large deformation conditions along its central axis to form an initial sample with a surface to be measured.

[0049] (2) Pretreatment: Mechanically grind the surface to be measured of the initial sample in step (1) successively with silicon carbide sandpapers of model 400#, 800#, and 1200# on an automatic grinding and polishing machine. After mechanical grinding, perform mechanical polishing. The loads used for mechanical grinding and mechanical polishing are the same. The polishing liquid is a suspension composed of an appropriate amount of 0.05μm Al 2 O 3 polishing paste and a certain amount of tap water. The fabric used for polishing is damping cloth. After mechanical polishing, rinse with water and then alcohol successively, and then dry with a hair dryer at room temperature to obtain a mechanically polished sample.

[0050] (3) Prepare an electrolytic polishing solution composed of 10 vol.% perchloric acid, 20 vol.% ethylene glycol, and 70 vol.% methanol, and naturally cool the electrolytic polishing solution to room temperature.

[0051] (4) Electrolytic polishing: Pour the electrolytic polishing solution obtained in step (3) into an electrolytic cell, invert the polished surface of the mechanically polished sample obtained in step (2) on the hole of the selected electrolytic cell cover, and press the voltage conducting head onto the non-polished surface of the specimen; then, set the polishing voltage to 20V, the polishing time to 20s, the exposed area to 0.5 cm 2 and the electrolyte flow rate to 12 m / s on the control panel of the microcomputer control system, save the electrolytic polishing program, and then click the start button to start the program for electrolytic polishing treatment; after the electrolytic polishing program is executed, immediately raise the voltage conducting head, take out the specimen, and immediately rinse with water and absolute ethanol successively, and dry with a hair dryer at room temperature to obtain a titanium alloy electrolytic polished sample with a smooth and flat polished area, as Figure 3 shown.

[0052] Example 3

[0053] This embodiment provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy, which specifically includes the following steps:

[0054] (1) Sample cutting: Use a wire electrical discharge machine to cut a near-β type TC18 titanium alloy disk sample after single-phase region hot deformation under high strain rate and large deformation conditions along its central axis to form an initial sample with a surface to be measured.

[0055] (2) Pretreatment: The test surface of the initial sample in step (1) is mechanically ground successively with silicon carbide sandpapers of model 400#, 800#, and 1200# on an automatic grinding and polishing machine. After mechanical grinding, mechanical polishing is carried out. The loads used for mechanical grinding and mechanical polishing are the same. The polishing liquid is a suspension composed of an appropriate amount of 0.05μm Al 2 O 3 polishing paste and a certain amount of tap water. The fabric used for polishing is damping cloth. After mechanical polishing, it is rinsed with water and then with alcohol successively, and then dried with a hair dryer at cold air to obtain a mechanically polished sample.

[0056] (3) Prepare an electrolytic polishing liquid composed of 8 vol.% perchloric acid and 92 vol.% absolute ethanol, and naturally cool the electrolytic polishing liquid to room temperature.

[0057] (4) Electrolytic polishing: Pour the electrolytic polishing liquid obtained in step (3) into the electrolytic cell. Invert the polished surface of the mechanically polished sample obtained in step (2) on the hole of the selected electrolytic cell cover, and press the voltage conducting head onto the non-polished surface of the sample; then, set the polishing voltage to 28V, the polishing time to 45s, the exposed area to 0.5 cm 2 and the electrolyte flow rate to 12 m / s on the control panel of the microcomputer control system, and then save the electrolytic polishing program. Immediately click the start button to start the program for electrolytic polishing treatment; after the electrolytic polishing program is executed, immediately raise the voltage conducting head, take out the sample and immediately rinse it with water and then with absolute ethanol successively, and dry it with a hair dryer at cold air to obtain a titanium alloy electrolytically polished sample with a smooth and flat polished area, as Figure 4 shown.

[0058] Example 4

[0059] This example provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy. The steps are the same as those in Example 1, except that:

[0060] In step (3), prepare an electrolytic polishing liquid composed of 3 vol.% perchloric acid, 25 vol.% n-butanol, and 72 vol.% methanol;

[0061] In step (4), set the polishing voltage to 50V, the polishing time to 50s, the exposed area to 0.5 cm 2 and the electrolyte flow rate to 13 m / s.

[0062] Example 5

[0063] This example provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy. The steps are the same as those in Example 1, except that:

[0064] In step (3), an electrolytic polishing solution composed of 10 vol.% perchloric acid, 50 vol.% n-butanol, and 40 vol.% methanol is prepared;

[0065] In step (4), a polishing voltage of 30 V, a polishing time of 15 s, an exposed area of 1 cm 2 and an electrolyte flow rate of 11 m / s are set.

[0066] Example 6

[0067] This example provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy. The steps are the same as those in Example 2, except that:

[0068] In step (3), an electrolytic polishing solution composed of 3 vol.% perchloric acid, 40 vol.% ethylene glycol, and 57 vol.% methanol is prepared;

[0069] In step (4), a polishing voltage of 30 V, a polishing time of 45 s, an exposed area of 0.5 cm 2 and an electrolyte flow rate of 13 m / s are set.

[0070] Example 7

[0071] This example provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy. The steps are the same as those in Example 2, except that:

[0072] In step (3), an electrolytic polishing solution composed of 10 vol.% perchloric acid, 20 vol.% ethylene glycol, and 70 vol.% methanol is prepared;

[0073] In step (4), a polishing voltage of 15 V, a polishing time of 20 s, an exposed area of 1 cm 2 and an electrolyte flow rate of 11 m / s are set.

[0074] Example 8

[0075] This example provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy. The steps are the same as those in Example 3, except that:

[0076] In step (3), an electrolytic polishing solution composed of 3 vol.% perchloric acid and 97 vol.% absolute ethanol is prepared;

[0077] In step (4), a polishing voltage of 40 V, a polishing time of 90 s, an exposed area of 0.5 cm 2 and an electrolyte flow rate of 13 m / s are set.

[0078] Example 9

[0079] This embodiment provides an electrolytic polishing method for preparing an EBSD specimen of a single-phase region hot-deformed near-β type titanium alloy. The steps are the same as those in Embodiment 3, except that:

[0080] In step (3), an electrolytic polishing solution composed of 10 vol.% perchloric acid and 90 vol.% absolute ethanol is prepared;

[0081] In step (4), the polishing voltage is 20 V, the polishing time is 20 s, the exposed area is 1 cm 2 and the electrolyte flow rate is 11 m / s.

[0082] The electrolytically polished samples in Embodiment 1, Embodiment 2, and Embodiment 3 are respectively calibrated using a scanning electron microscope equipped with an EBSD probe. The IPF maps generated thereby respectively correspond to Figure 5 , Figure 6 and Figure 7 , and the resolution rates are 86%, 88%, and 94% respectively.

[0083] Comparing Embodiment 1, Embodiment 2, and Embodiment 3, it can be seen that in the IPF map of Embodiment 1, there are a certain number of uncalibrated data points on the elongated grain boundaries; in the IPF map of Embodiment 2, the number of uncalibrated data points on the elongated grain boundaries is significantly reduced; in Embodiment 3, almost all grains are well calibrated, and the resolution rate of the obtained EBSD sample is the highest, indicating that the electrolyte composition and electrolytic polishing parameters used in Embodiment 3 are most suitable for preparing EBSD samples of the near-β type TC18 titanium alloy after single-phase region hot deformation under high strain rate and large deformation conditions.

[0084] The electrolytically polished samples in Embodiment 4-9 are respectively calibrated using a scanning electron microscope equipped with an EBSD probe. Their IPF maps are successively as Figures 8 - 13 shown, and the obtained sample resolution rates are not lower than 86%, having a high resolution rate and meeting the requirements of EBSD specimens.

[0085] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An electrolytic polishing method for preparing single-phase hot-deformed near-β-type titanium alloy EBSD specimens, characterized in that: The steps include: The surface to be tested of the single-phase region heat-deformed near-β-type titanium alloy EBSD sample is mechanically ground and mechanically polished, and then electrolytically polished in an electrolytic polishing solution that is pre-configured and naturally cooled to room temperature to obtain a single-phase region heat-deformed near-β-type titanium alloy EBSD sample; the composition of the electrolytic polishing solution and the parameters of the electrolytic polishing are any of the following three: (1) Electrolytic polishing liquid composition: 3-10 vol.% perchloric acid, 25-50 vol.% n-butanol and 40-72 vol.% methanol; polishing voltage: 30-50 V, polishing time: 15-50 s, the area of ​​the sample surface exposed to the electrolytic polishing solution: 0.5-1 cm 2 , electrolyte flow rate: 11~13m / s; (2) Electrolytic polishing liquid composition: 3-10 vol.% perchloric acid, 20-40 vol.% ethylene glycol and 57-70 vol.% methanol; polishing voltage: 15-30 V, polishing time: 20-45 s, area of ​​the sample surface exposed to the electrolytic polishing liquid: 0.5-1 cm 2 , electrolyte flow rate: 11~13m / s; (3) Electrolytic polishing liquid composition: 3-10 vol.% perchloric acid and 90-97 vol.% anhydrous ethanol; polishing voltage: 20-40 V, polishing time: 20-90 s, the area of ​​the sample surface exposed to the electrolytic polishing solution: 0.5-1 cm 2 , electrolyte flow rate: 11~13m / s.

2. The electrolytic polishing method for preparing a single-phase hot-deformed near-β-type titanium alloy EBSD specimen according to claim 1, characterized in that: The single-phase region heat-deformed near-β-type titanium alloy EBSD sample before mechanical grinding is obtained by cutting the near-β-type titanium alloy sample after heat deformation in the single-phase region to form an initial sample with a surface to be tested.

3. The electrolytic polishing method for preparing a single-phase hot-deformed near-β-type titanium alloy EBSD specimen according to claim 2, characterized in that: The mechanical grinding is to grind the test surface of the initial sample with 400#, 800# and 1200# silicon carbide sandpaper in sequence.

4. The electrolytic polishing method for preparing a single-phase hot-deformed near-β-type titanium alloy EBSD specimen according to claim 3, characterized in that: The polishing liquid used in the mechanical polishing is Al2O3 suspension, and the fabric used in the mechanical polishing is damping cloth; after the mechanical polishing, the sample is rinsed with water and alcohol in sequence and dried to obtain the mechanically polished sample.

5. The electrolytic polishing method for preparing a single-phase hot-deformed near-β-type titanium alloy EBSD specimen according to claim 4, characterized in that: The Al2O3 suspension is a suspension consisting of Al2O3 polishing paste with a finest particle size of 0.05 μm and water.

6. The electrolytic polishing method for preparing a single-phase hot-deformed near-β-type titanium alloy EBSD specimen according to claim 1, characterized in that: In the first type, the electrolytic polishing solution consists of: 5-10 vol.% perchloric acid, 35-50 vol.% n-butanol and 40-60 vol.% methanol; polishing voltage: 35-50 V, polishing time: 20-50 s, the area of ​​the sample surface exposed to the electrolytic polishing solution: 0.5-1 cm 2 , electrolyte flow rate: 12~13m / s.

7. The electrolytic polishing method for preparing a single-phase hot-deformed near-β-type titanium alloy EBSD specimen according to claim 1, characterized in that: In type (2), the electrolytic polishing solution consists of: 10vol.% perchloric acid, 20-25vol.% ethylene glycol and 65-70vol.% methanol; polishing voltage: 20-30V, polishing time: 20-45s, the area of ​​the sample surface exposed to the electrolytic polishing solution: 0.5-1cm 2 , electrolyte flow rate: 12~13m / s.

8. The electrolytic polishing method for preparing a single-phase hot-deformed near-β-type titanium alloy EBSD specimen according to claim 1, characterized in that: In the third type, the electrolytic polishing solution comprises: 8-10 vol.% perchloric acid and 90-92 vol.% anhydrous ethanol; Polishing voltage: 28-40V, polishing time: 20-45s, the area of ​​the sample surface exposed to the electrolytic polishing liquid: 0.5-1cm 2 , electrolyte flow rate: 12~13m / s.

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