Method for detecting content of each composition phase of double-phase titanium alloy

Abstract

The invention relates to the technical field of titanium alloy detection, in particular to a method for detecting the content of each component phase of a double-phase titanium alloy, which comprises the following steps: S1, sampling: cutting a titanium alloy sample; s2, mechanical polishing treatment: carrying out mechanical grinding and polishing on the analysis surface of the sample, and cleaning; s3, electrolytic polishing: carrying out electrolytic polishing on the sample; s4, the polished sample is observed under an optical metallographic microscope, and the surface of the sample should be smooth, flat, free of scratches and free of burns; if the scratches or burns occur, the step S2 to the step S4 are repeated; and S5, adjusting parameters of the scanning electron microscope and the EBSD probe, and detecting the sample to obtain the specific contents of the alpha phase and the beta phase in the detection area. The method provided by the invention has the advantages of high detection efficiency and high measurement precision, and can completely eliminate the influence of human factors.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy detection, and in particular to a method for detecting the content of each constituent phase of a dual-phase titanium alloy. Background Art

[0002] Titanium alloys have low density, high specific strength, wide operating temperature range, medium corrosion resistance and good biocompatibility. Most dual-phase titanium alloys are mainly composed of primary α phase and β phase, and the content of each phase has a direct impact on the performance of titanium alloys. Studies have shown that the content of primary α phase is directly related to the plasticity of titanium alloys. The higher the primary α phase, the better the plasticity. As the solution temperature of titanium alloys increases, the content of primary α phase decreases, the content of metastable phase increases, and the strength of the alloy increases. Therefore, it is of great significance to study the content of each phase in titanium alloys.

[0003] The high and low magnification microstructure inspection of titanium and titanium alloys follows the standard GB / T 5168-2020. Currently, this standard only has relevant measurement methods for the content of α phase in titanium alloys, and cannot detect the content of β phase in the sample. At present, the content of α phase is determined by the traditional corrosion comparison method or grid measurement method. After corrosion, the sample is interfered by the sample mass and corrosion film, and the measured value deviates from the actual value, which is not conducive to subsequent accurate measurement; the comparison method is greatly affected by human subjective factors and has large errors; the grid measurement is less efficient and has higher requirements on sample preparation quality.

[0004] Based on the above reasons, the present invention proposes a method for detecting the content of each constituent phase of a duplex titanium alloy. Summary of the invention

[0005] The main purpose of the present invention is to propose a method for detecting the content of each constituent phase of a duplex titanium alloy, eliminate the interference of corrosion film and human measurement errors in the traditional sample preparation process, improve the detection accuracy, and aim to solve the above technical problems.

[0006] To achieve the above object, the present invention proposes a method for detecting the content of each constituent phase of a dual-phase titanium alloy, the steps comprising:

[0007] S1. Sampling: cutting titanium alloy samples;

[0008] S2. Mechanical polishing: Mechanically grind and polish the sample analysis surface, and clean it;

[0009] S3, electrolytic polishing: electrolytic polishing the sample;

[0010] S4. Observe the polished sample under an optical metallographic microscope. The surface of the sample should be smooth and flat without scratches or burns. If scratches or burns are found, repeat steps S2 to S4.

[0011] S5. Adjust the parameters of the scanning electron microscope and EBSD probe, detect the sample, and obtain the specific content of the α phase and β phase in the detection area.

[0012] Preferably, in step S1, when cutting the titanium alloy sample.

[0013] Preferably, in step S1, when cutting the titanium alloy sample, the sampling process should be sufficiently cooled to avoid the formation of a heat affected zone. If a heat affected zone exists, the heat affected zone needs to be completely removed or resampled.

[0014] Preferably, in step S2, the analysis surface of the sample is mechanically ground and polished so that the sample surface presents mirror features and no obvious grinding and polishing marks are found by visual inspection.

[0015] Preferably, in step S2, the sample after mechanical polishing is cleaned with anhydrous ethanol in an ultrasonic cleaner, the cleaning time is 10 to 12 minutes, and the temperature is 20° C. to 25° C.; after cleaning, the sample is blown dry with dry hot air.

[0016] Preferably, in step S3, acetic acid and perchloric acid solutions are used for electrolytic polishing, and the ratio of the two is: 1000 ml of acetic acid and 65 ml of perchloric acid; liquid nitrogen cooling is used during polishing, the polishing voltage is 38 to 42 V, and the polishing time is 40 to 50 s; to obtain a stress-free sample.

[0017] Preferably, in step S5, the voltage of the scanning electron microscope is adjusted to 25KV, and the aperture is selected to be 60um.

[0018] Preferably, in step S5, the stage is adjusted so that the sample observation surface is 70° to the vertical direction; secondary electron observation is adopted, and the stage distance is adjusted so that the working distance after clear focus when the sample surface is magnified 500 times is 8±0.5 mm, and the magnification is maintained at 500 times.

[0019] Preferably, in step S5, the parameters of the EBSD probe are adjusted so that the horizontal distance between the probe and the sample surface is ≤8 mm.

[0020] Preferably, in step S5, the observation signal intensity of the EBSD probe is made ≥85% by shortening the working distance of the electron microscope stage, shortening the horizontal distance between the EBSD probe and the sample surface, and increasing the voltage; click to collect the image to obtain a clear Kikuchi pattern image on the sample surface, select the entire field of view as the collection area, set the scanning step to 0.22um, and merge the pixels to 4×4 to obtain the surface distribution position of each phase collected and calculate the content of each phase.

[0021] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0022] (1) By adopting the method for detecting the content of each component phase of the dual-phase titanium alloy provided by the present invention, when the incident high-voltage electron beam in the scanning electron microscope bombards the sample surface, some electrons will escape from the sample surface due to the large scattering angle. When these electrons meet the Bragg diffraction conditions, diffraction phenomenon will occur, and Kikuchi patterns will appear. These Kikuchi patterns can be collected by using an EBSD probe. According to the characteristics of the Kikuchi patterns, the interplanar spacing and the angle between the crystal planes can be calculated. The α phase in the titanium alloy is a close-packed hexagonal crystal structure, and the β phase is a face-centered cubic crystal structure. There are obvious differences in the interplanar spacing and the interplanar angle between the α phase and the β phase. Therefore, the percentage of the α phase and the β phase can be calculated by this method.

[0023] (2) The method proposed by the present invention has high detection efficiency and high measurement accuracy, and can completely eliminate the influence of human factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the distribution of various phases in titanium alloy. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] A method for detecting the content of each component phase of a dual-phase titanium alloy, comprising the following steps:

[0027] S1. Sampling: Cut titanium alloy samples of suitable size as needed. The length, width and height of the samples shall not exceed 12mm. The sampling process should be fully cooled to avoid the formation of heat-affected zones. If a heat-affected zone exists, it needs to be completely removed or re-sampled.

[0028] S2. Mechanical polishing: Mechanically grind and polish the sample analysis surface, and clean it; specifically: Mechanical grinding and polishing make the sample analysis surface present mirror characteristics, and visual inspection shows no obvious grinding and polishing marks. Clean the sample after mechanical polishing with anhydrous ethanol in an ultrasonic cleaner, the cleaning time is 10 to 12 minutes, the temperature is 20℃ to 25℃; after cleaning, use dry hot air to blow dry the sample.

[0029] S3. Electrolytic polishing: The sample is electropolished; specifically: 1000ml of acetic acid + 65ml of perchloric acid solution is used for electrolytic polishing, liquid nitrogen cooling is used during polishing, the polishing voltage is 38-42V, and the polishing time is 40-50s; to obtain a stress-free sample.

[0030] S4. Observe the polished sample under an optical metallographic microscope. The surface of the sample should be smooth and flat without scratches or burns. If scratches or burns are found, repeat steps S2 to S4.

[0031] S5, adjusting the parameters of the scanning electron microscope and the EBSD probe, testing the sample, and obtaining the specific content of the α phase and the β phase in the test area. Specifically, step S5 includes:

[0032] S501. Adjust the voltage of the scanning electron microscope to 25KV and the aperture to 60um. Adjust the stage so that the sample observation surface is 70° to the vertical direction; use secondary electron observation, and adjust the stage distance so that the working distance after the sample surface is clearly focused when it is magnified 500 times is 8±0.5mm, and keep the magnification at 500 times.

[0033] S502, adjust the parameters of the EBSD probe so that the horizontal distance between the probe and the sample surface is ≤8mm, select the α phase and β phase in the database; shorten the working distance of the electron microscope stage, shorten the horizontal distance between the EBSD probe and the sample surface, and increase the voltage to make the observation signal intensity of the EBSD probe ≥85%. Click to collect images to obtain a clear Kikuchi pattern image on the sample surface, select the entire field of view as the collection area, set the scanning step to 0.22um, and merge the pixels to 4×4, obtain the surface distribution position of each phase collected and calculate the content of each phase. See the table below and Figure 1 The following table shows Figure 1 The percentage of each phase in Figure 1 In the figure, red is the α phase, blue is the β phase, and the gray-white point is the zero resolution point.

[0034]

[0035] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for detecting the content of each component phase of a dual-phase titanium alloy, characterized in that the steps include: S1. Sampling: cutting titanium alloy samples; S2. Mechanical polishing: Mechanically grind and polish the sample analysis surface, and clean it; S3, electrolytic polishing: electrolytic polishing the sample; S4. Observe the polished sample under an optical metallographic microscope. The surface of the sample should be smooth and flat without scratches or burns. If scratches or burns are found, repeat steps S2 to S4. S5. Adjust the parameters of the scanning electron microscope and EBSD probe, detect the sample, and obtain the specific content of the α phase and β phase in the detection area.

2. A method for detecting the content of each constituent phase of a dual-phase titanium alloy as claimed in claim 1, characterized in that: In step S1, when cutting the titanium alloy sample, the length, width and height of the sample are not greater than 12 mm.

3. A method for detecting the content of each constituent phase of a dual-phase titanium alloy as claimed in claim 1, characterized in that: In step S1, when cutting the titanium alloy sample, the sampling process should be cooled sufficiently to avoid the formation of a heat-affected zone. If a heat-affected zone exists, the heat-affected zone needs to be completely removed or resampled.

4. A method for detecting the content of each constituent phase of a dual-phase titanium alloy as claimed in claim 1, characterized in that: In step S2, the analysis surface of the sample is mechanically ground and polished so that the sample surface presents mirror features and no obvious grinding and polishing marks are found by visual inspection.

5. The method for detecting the content of each constituent phase of a dual-phase titanium alloy according to claim 1, characterized in that: In the step S2, the sample after mechanical polishing is cleaned with anhydrous ethanol in an ultrasonic cleaner, the cleaning time is 10 to 12 minutes, and the temperature is 20° C. to 25° C.; after cleaning, the sample is blown dry with dry hot air.

6. A method for detecting the content of each constituent phase of a dual-phase titanium alloy as claimed in claim 1, characterized in that: In step S3, electrolytic polishing is performed using acetic acid and perchloric acid solutions in a ratio of 1000 ml acetic acid to 65 ml perchloric acid; liquid nitrogen cooling is used during polishing, the polishing voltage is 38 to 42 V, and the polishing time is 40 to 50 s; to obtain a stress-free sample.

7. A method for detecting the content of each constituent phase of a dual-phase titanium alloy as claimed in claim 1, characterized in that: In step S5, the voltage of the scanning electron microscope is adjusted to 25KV, and the aperture is selected to be 60um.

8. A method for detecting the content of each constituent phase of a dual-phase titanium alloy as claimed in claim 1, characterized in that: In step S5, the stage is adjusted so that the sample observation surface is 70° to the vertical direction; secondary electron observation is adopted, and the stage distance is adjusted so that the working distance after clear focus when the sample surface is magnified 500 times is 8±0.5mm, and the magnification is maintained at 500 times.

9. A method for detecting the content of each constituent phase of a dual-phase titanium alloy as claimed in claim 1, characterized in that: In step S5, the parameters of the EBSD probe are adjusted so that the horizontal distance between the probe and the sample surface is ≤8 mm.

10. A method for detecting the content of each constituent phase of a dual-phase titanium alloy as claimed in claim 9, characterized in that: In step S5, the observation signal intensity of the EBSD probe is made ≥85% by shortening the working distance of the electron microscope stage, shortening the horizontal distance between the EBSD probe and the sample surface, and increasing the voltage; click to collect the image to obtain a clear Kikuchi pattern image on the sample surface, select the entire field of view as the collection area, set the scanning step to 0.22um, and merge the pixels to 4×4 to obtain the surface distribution position of each phase collected and calculate the content of each phase.

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