A method for determining beta phase transformation temperature in titanium alloy by scanning electron microscope

Abstract

The application discloses a method for measuring beta phase transition temperature in a titanium alloy by using a scanning electron microscope, and comprises the following steps: cutting a test sample of the titanium alloy; quenching and heat treating the test sample by using a heat treatment furnace according to a preset temperature interval near a theoretical beta phase transition temperature of the test sample of the titanium alloy; mechanically grinding and polishing the test sample until the surface reaches a mirror surface and no obvious scratches are observed under an optical microscope, so that a test surface of the sample is obtained; etching the test surface of the sample by using an etching liquid to obtain a detection surface with clear microstructure; analyzing microstructure and chemical composition of the test sample by using a scanning electron microscope and an energy spectrometer to obtain alpha phase and beta phase contents in the test sample of the titanium alloy; and determining the beta phase transition temperature of the titanium alloy by using a scanning electron microscope picture comparison method. The method has the advantages of intuitive measurement results and high accuracy by combining the advantages of the scanning electron microscope and the energy spectrometer, and provides a new method for measuring the beta phase transition temperature in the titanium alloy.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy analysis and testing technology, and in particular to a method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy. Background Technology

[0002] The β-phase transformation temperature in titanium alloys is a crucial parameter in phase diagram studies, essential for hot working and heat treatment, and serves as a vital basis for formulating processing techniques and selecting deformation parameters. Currently, methods for testing the β-phase transformation temperature in titanium alloys include metallographic methods (GB / T 23605-2020, HB 6623.2-1992), differential thermal analysis (HB 6623.1-1992), thermal expansion methods, electrical resistance methods, high-temperature X-ray methods, and calculation methods.

[0003] The above methods have the following problems: 1) The calculation method is based on the influence of each element in the alloy on the β phase transformation temperature, and the result is obtained by empirical formula. The error of composition testing and empirical formula cannot be eliminated during the calculation. The result can only be used as a reference and cannot be applied to industrial production; 2) Differential thermal analysis, thermal expansion method, resistance method, and high-temperature X-ray method are all tested during the material heating process. However, the phase transformation process of titanium alloys gradually increases with the increase of alloy element content. Therefore, these four methods can only measure the real-time phase transformation process of titanium alloys and cannot obtain the minimum temperature at which the material completely transforms into the β phase structure. The data values ​​obtained are usually too high; X-ray method analyzes the phase transformation temperature of the material by comparing the changes in the peak shape of the diffraction pattern with the change of hydrogen content. When the content of a phase is lower than a certain limit (about 1% to 10%, which varies for different phases), the presence of that phase cannot be detected. Therefore, none of these methods have been adopted in industrial production. Only differential thermal analysis has formed an industry standard, HB 6623.1-1992. This standard also clearly states that this method is suitable for titanium alloys with low alloy element content (industrial pure titanium, α-type titanium alloys). For titanium alloys with high alloy element content (two-phase titanium alloys, β-titanium alloys), the standard notes that "judgment is difficult." 3) Metallography determines the phase transformation point of titanium alloys by observing the metallographic structure of samples after quenching at different temperatures according to a preset temperature interval using a metallographic microscope. Therefore, metallography is completely unaffected by the length of the phase transformation process and can reflect the lowest temperature at which the material completely transforms into the β-phase structure, making it accurate and reliable. However, in actual production, although there is a corresponding standard (GB / T 23605-2020) for metallographic testing of the β-phase transformation temperature in titanium alloys, the magnification of metallographic microscopes is limited, the resolution is low, the depth of field is small (2-3μm), and there are high requirements for the flatness of the sample surface.

[0004] Therefore, there is an urgent need to develop a characterization technique that addresses the shortcomings of existing technologies. Compared to metallurgical microscopes, scanning electron microscopes offer a wider range of adjustable magnification, higher image resolution, and greater depth of field (several millimeters), producing images with richer three-dimensionality and providing more comprehensive sample information. When paired with an energy dispersive spectroscopy (EDS) instrument, they can simultaneously observe the microstructure morphology and perform micro-area composition analysis, accurately identifying the α and β phases in titanium alloys and thus obtaining the precise β phase transformation temperature. Summary of the Invention

[0005] The purpose of this invention is to provide a method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy. By combining the advantages of scanning electron microscopy and energy dispersive spectroscopy, the method enables observation of microstructure morphology and analysis of micro-area chemical composition, allowing for a more intuitive and accurate determination of the β-phase transformation temperature in titanium alloys.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy, the method comprising the following steps:

[0008] S1, cut the titanium alloy sample to be tested;

[0009] S2, near the theoretical transformation temperature of the β phase of the titanium alloy test sample, the test sample is subjected to quenching heat treatment in a heat treatment furnace according to the preset temperature interval.

[0010] S3. Mechanical grinding and polishing are performed on the test sample until the surface of the test sample reaches a mirror finish and no obvious scratches are observed under an optical microscope, thus obtaining the test surface of the sample.

[0011] S4, the test surface of the sample is etched to obtain a test surface with clear microstructure;

[0012] S5. Based on the detection surface, the microstructure and chemical composition of the sample to be tested are analyzed by scanning electron microscopy and energy dispersive spectroscopy to obtain the content of α phase and β phase in the titanium alloy sample to be tested.

[0013] S6. Based on the content of α and β phases, the β phase transformation temperature of titanium alloys is determined by comparing scanning electron microscopy images.

[0014] Further, in step S1, cutting the titanium alloy sample to be tested specifically includes:

[0015] The titanium alloys include α-type, α-β-type and metastable β-type titanium alloys, and the materials of the titanium alloys are intermediate billets, processed products or hot hydrogen-treated samples.

[0016] The cutting criteria for the test sample are to avoid altering the original microstructure of the titanium alloy, and the sample surface should be polished.

[0017] The test sample is a cylinder with a diameter of 10mm to 12mm and a height of 10mm, or a cuboid with a side length of 10mm to 12mm and a height of 10mm.

[0018] Multiple test samples are grouped together and taken from the same processing stage of the product.

[0019] Further, in step S2, near the theoretical transformation temperature of the β phase of the titanium alloy test sample, the test sample is subjected to quenching heat treatment in a heat treatment furnace according to a preset temperature interval, specifically including:

[0020] Near the theoretical transformation temperature of the β phase of the titanium alloy test sample, several test temperature points were selected, and multiple test samples were sequentially subjected to quenching heat treatment in a heat treatment furnace at a preset temperature interval of 10℃.

[0021] Furthermore, the heat treatment furnace is a box-type resistance furnace or a tube-type resistance furnace. The box-type resistance furnace has the function of loading a load thermocouple, and the furnace temperature uniformity of the effective working area of ​​the box-type resistance furnace or the tube-type resistance furnace is not less than 3°C.

[0022] During the quenching heat treatment, the holding time of the test sample is 20-40 minutes. The holding time is calculated from the time the effective working area of ​​the furnace reaches the set temperature. After the holding time is completed, the test sample is quickly taken out and immediately placed in a water tank for quenching. The quenching water temperature is not higher than 25°C and the quenching delay time is not more than 3 seconds. If a load thermocouple is used, the temperature displayed by the load thermocouple at the end of the holding time is taken as the actual temperature of the test sample.

[0023] Further, step S3 involves mechanically grinding and polishing the sample until its surface reaches a mirror finish and shows no obvious scratches under an optical microscope, thus obtaining the test surface of the sample. Specifically, this includes:

[0024] The standard for mechanical grinding is that at least 2 mm of oxide layer must be removed from the surface of the test sample to ensure complete removal of the oxide layer.

[0025] Select sandpaper with a grit size ranging from coarse to fine for metallographic grinding of the test sample;

[0026] The test sample was further polished using SiO2 polishing slurry until the surface of the test sample reached a mirror finish and no obvious scratches were observed under different magnifications of an optical microscope, thus obtaining the test surface of the sample.

[0027] Furthermore, in step S4, the surface of the sample to be tested is etched to obtain a test surface with a clear microstructure, specifically including:

[0028] A mixed acid solution was selected as the corrosive agent, and the volume fraction of the mixed acid solution was HF:HNO3:H2O = 1:3:7.

[0029] The sample surface to be tested is immersed in the etching solution and etched for several seconds to obtain a test surface with a clear microstructure.

[0030] Further, in step S5, based on the detection surface, the microstructure morphology and chemical composition of the test sample are analyzed by scanning electron microscopy and energy dispersive spectroscopy to obtain the content of α-phase and β-phase in the titanium alloy test sample, specifically including:

[0031] Based on the scanning electron microscope and energy dispersive spectroscopy (EDS) attachment, the detection surface is observed by setting test parameters to obtain the microstructure morphology and chemical composition data of the test sample, and the content of α phase and β phase in the titanium alloy test sample is analyzed. The test parameters include accelerating voltage, working distance, scanning image size, image magnification, and energy dispersive spectroscopy acquisition time.

[0032] Furthermore, obtaining the microstructure morphology of the test sample includes:

[0033] Observe at least five fields of view at the center and half the radius of the sample to be tested, and take microscopic tissue images of representative fields of view as needed.

[0034] Further, step S6, determining the β-phase transformation temperature of the titanium alloy based on the α-phase and β-phase content using a scanning electron microscope (SEM) image comparison method, specifically includes:

[0035] Compare the microstructure images of the test samples after different quenching heat treatment temperatures, wherein the microstructure images are secondary electron images or backscattered electron images;

[0036] When the α phase content in the microstructure decreases from 1% to 0%, for titanium alloys with a β phase transformation temperature range of no more than 10℃, the β phase transformation temperature is the average of the heat treatment temperature represented by the test sample with an α phase content of 0% and the heat treatment temperature represented by the adjacent sample with an α phase content greater than 0%.

[0037] When the α phase content in the microstructure decreases from 1% to 0%, for titanium alloys with a β phase transformation temperature range greater than 10°C, the β phase transformation temperature is the average of the highest heat treatment temperature represented by the test sample with an α phase content greater than 0% and the adjacent lower heat treatment temperature, and the result is rounded to the nearest integer.

[0038] Furthermore, in step S6, when determining the β-phase transformation temperature of the titanium alloy by comparing scanning electron microscope (SEM) images, the SEM images of different samples are taken at the same magnification.

[0039] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: The method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy provided by the present invention has the following beneficial effects compared with the prior art:

[0040] The microstructure and chemical composition of titanium alloys were obtained using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The β-phase transformation temperature of the titanium alloys was determined by comparing SEM images. Specifically, when the α-phase content in the microstructure decreased from 1% to 0%, the β-phase transformation temperature range was determined based on whether it was greater than 10℃. If it was not greater, the β-phase transformation temperature was the average of the heat treatment temperature represented by the sample with 0% α-phase content and the heat treatment temperature represented by the adjacent sample with α-phase content greater than 0%. If it was greater, the β-phase transformation temperature was the average of the highest heat treatment temperature represented by the sample with α-phase content greater than 0% and the adjacent lower heat treatment temperature. The results were rounded to integers.

[0041] As can be seen, this invention combines the advantages of scanning electron microscopy and energy dispersive spectroscopy, and has the advantages of intuitive measurement results and high accuracy, providing a new method for testing the β phase transformation temperature in titanium alloys. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a flowchart of the method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy according to the present invention;

[0044] Figure 2 The images shown are micrographs of the original TC17 sample from an embodiment of the present invention, wherein (a) is a secondary electron image and (b) is a backscattered electron image.

[0045] Figure 3 The microstructure composition of the original TC17 sample in this embodiment of the invention is shown in (a) backscattered electron image, (b) schematic diagram of α phase composition, and (c) schematic diagram of β phase composition.

[0046] Figure 4 The images shown are microscopic images of the tissue after heat treatment at 890℃ according to an embodiment of the present invention. (a) is a secondary electron image, and (b) is a backscattered electron image.

[0047] Figure 5 The microstructure composition after heat treatment at 890℃ in an embodiment of the present invention is shown in (a) a backscattered electron image, (b) a schematic diagram of the α phase composition, and (c) a schematic diagram of the β phase composition.

[0048] Figure 6These are microscopic images of the tissue after heat treatment at 900℃ according to an embodiment of the present invention, wherein (a) is a secondary electron image and (b) is a backscattered electron image;

[0049] Figure 7 These are microscopic images of the tissue after heat treatment at 910℃ according to an embodiment of the present invention, wherein (a) is a secondary electron image and (b) is a backscattered electron image. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] The purpose of this invention is to combine the advantages of scanning electron microscopy and energy dispersive spectroscopy to observe the microstructure morphology and analyze the composition of micro-areas, providing a new method for testing the β-phase transformation temperature in titanium alloys.

[0052] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] like Figure 1 As shown, the method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy provided by this invention includes the following steps:

[0054] S1, cut the titanium alloy sample to be tested;

[0055] S2, near the theoretical transformation temperature of the β phase of the titanium alloy test sample, the test sample is subjected to quenching heat treatment in a heat treatment furnace according to the preset temperature interval.

[0056] S3. Mechanical grinding and polishing are performed on the test sample until the surface of the test sample reaches a mirror finish and no obvious scratches are observed under an optical microscope, thus obtaining the test surface of the sample.

[0057] S4, the test surface of the sample is etched to obtain a test surface with clear microstructure;

[0058] S5. Based on the detection surface, the microstructure and chemical composition of the sample to be tested are analyzed by scanning electron microscopy and energy dispersive spectroscopy to obtain the content of α phase and β phase in the titanium alloy sample to be tested.

[0059] S6. Based on the content of α and β phases, the β phase transformation temperature of titanium alloys is determined by comparing scanning electron microscopy images.

[0060] Specifically, step S1 includes:

[0061] The titanium alloys include α-type, α-β-type, and metastable β-type titanium alloys. The materials of the titanium alloys are intermediate billets, processed products, or hot hydrogen-treated samples. For example, intermediate billets include cast billets, forged billets, slabs, etc., and processed products include bars, plates, etc.

[0062] The cutting criteria for the test sample are to avoid altering the original microstructure of the titanium alloy, and the sample surface should be polished.

[0063] The test sample is a cylinder with a diameter of 10mm to 12mm and a height of about 10mm, or a cuboid with a side length of 10mm to 12mm and a height of about 10mm.

[0064] Multiple test samples are grouped together and taken from the same processing stage of the product.

[0065] Step S2 specifically includes:

[0066] Within a temperature range near the theoretical β-phase transformation temperature of the titanium alloy test sample (e.g., several adjacent temperatures with the same temperature difference above the transformation temperature or several adjacent temperatures with the same temperature difference below the transformation temperature), several test temperature points (e.g., 5 points) are selected. Multiple test samples are then sequentially subjected to quenching heat treatment in a heat treatment furnace at preset temperature intervals of 10°C. Furthermore, the temperature intervals and test temperature points can be appropriately increased or decreased in the initial stage, while ensuring the accuracy of the test results.

[0067] For example, the heat treatment furnace is a box-type resistance furnace or a tube-type resistance furnace. The box-type resistance furnace has the function of loading a load thermocouple, and the furnace temperature uniformity of the effective working area of ​​the box-type resistance furnace or the tube-type resistance furnace is not less than 3°C.

[0068] During the quenching heat treatment, the holding time of the test sample is 20-40 minutes. The holding time is calculated from the time the effective working area of ​​the furnace reaches the set temperature. After the holding time is completed, the test sample is quickly taken out and immediately placed in a water tank for quenching. The quenching water temperature is not higher than 25°C and the quenching delay time is not more than 3 seconds. If a load thermocouple is used, the temperature displayed by the load thermocouple at the end of the holding time is taken as the actual temperature of the test sample.

[0069] Step S3 specifically includes:

[0070] The standard for mechanical grinding is that at least 2 mm of oxide layer must be removed from the surface of the test sample to ensure complete removal of the oxide layer.

[0071] Select sandpaper with a grit size ranging from coarse to fine for metallographic grinding of the test sample;

[0072] The test sample was further polished using SiO2 polishing slurry until the surface of the test sample reached a mirror finish and no obvious scratches were observed under different magnifications of an optical microscope, thus obtaining the test surface of the sample.

[0073] Step S4 specifically includes:

[0074] A suitable etching solution is selected as a mixed acid solution, with a volume fraction of HF:HNO3:H2O = 1:3:7; after immersion etching for several seconds, a detection surface with clear microstructure is obtained.

[0075] In step S5, during the process of obtaining the microstructure morphology and chemical composition, the testing surface of the sample is observed by setting test parameters using the scanning electron microscope and energy dispersive spectroscopy (EDS) attachments. This allows for the acquisition of microstructure morphology and chemical composition data, and precise analysis of the microstructure composition (α-phase and β-phase content) in the titanium alloy sample. The test parameters include accelerating voltage, working distance, scanning image size, image magnification, and EDS acquisition time.

[0076] The process of obtaining microstructure morphology in step S5 should take into account the influence of microscopic composition fluctuations in different parts of the sample on the microstructure. At least five fields of view should be observed at the center and half radius of the sample. Representative fields of view should be selected as needed to take microstructure images.

[0077] Step S6, based on the α-phase and β-phase content, determines the β-phase transformation temperature of the titanium alloy by comparing scanning electron microscopy images, specifically including:

[0078] Compare the microstructure images of the test samples after different quenching heat treatment temperatures, wherein the microstructure images are secondary electron images or backscattered electron images;

[0079] When the α phase content in the microstructure decreases from 1% to 0%, for titanium alloys with a β phase transformation temperature range of no more than 10℃, the β phase transformation temperature is the average of the heat treatment temperature represented by the test sample with an α phase content of 0% and the heat treatment temperature represented by the adjacent sample with an α phase content greater than 0%.

[0080] When the α phase content in the microstructure decreases from 1% to 0%, for titanium alloys with a β phase transformation temperature range greater than 10°C, the β phase transformation temperature is the average of the highest heat treatment temperature represented by the test sample with an α phase content greater than 0% and the adjacent lower heat treatment temperature, and the result is rounded to the nearest integer.

[0081] In step S6, when determining the β-phase transformation temperature of the titanium alloy by comparing scanning electron microscope (SEM) images, the SEM images of different samples are taken at the same magnification.

[0082] Specifically, taking TC17 titanium alloy as an example, the method for determining the β-phase transformation temperature in titanium alloy using scanning electron microscopy is described. This embodiment includes the following steps:

[0083] S1. Using wire cutting equipment, six cylindrical test samples with a diameter of 10mm and a height of 10mm were cut from the TC17 titanium alloy ingot. The surfaces of the test samples were then polished.

[0084] S2. Near the theoretical β-phase transformation temperature of the TC17 titanium alloy test sample, five heating temperature points of 880℃, 890℃, 900℃, 910℃ and 920℃ were set. The test sample was placed in a tube resistance furnace and held for 30 minutes before being quickly water quenched.

[0085] S3. SiC sandpaper with different mesh sizes from coarse to fine was selected to mechanically grind the sample to be tested. Then, SiO2 polishing liquid with a particle size of 0.05μm was used to further polish the sample until the surface of the sample to be tested was mirror-like and no obvious scratches were observed under different magnifications of an optical microscope.

[0086] S4, using a mixed acid solution (HF:HNO3:H2O=1:3:7 (volume fraction)), after immersion and etching for 10 seconds, a clear detection surface of microstructure is obtained;

[0087] S5. Using scanning electron microscopy and energy dispersive spectroscopy, the microstructure and chemical composition of the TC17 titanium alloy sample were obtained. The original TC17 sample microstructure consisted of equiaxed primary α phase and β-transformation microstructure containing acicular α phase (e.g., ...). Figure 2 As shown), Figure 3 As shown, the α phase is rich in Al (aluminum), and the β phase is rich in Mo (molybdenum) and Cr (chromium). Therefore, in the backscattered electron image, the α phase appears gray and the β phase appears bright white.

[0088] S6, observe the microscopic tissue image, and you can obtain 890℃ (e.g. Figure 4 (as shown) and 900℃ (as shown) Figure 6 The microstructure after heat treatment (as shown) consists of primary α phase (appearing grayish-black in backscattered electron microscopy) and β phase, and β grain boundaries can be observed. After heat treatment at 910℃, the β grain boundaries are clearly visible, and the primary α phase (as shown) is not observed. Figure 7 (As shown). Therefore, the β-phase transition temperature of this sample can be determined to be 905℃.

[0089] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy, characterized in that, Includes the following steps: S1, cut the titanium alloy sample to be tested; S2, near the theoretical transformation temperature of the β phase of the titanium alloy test sample, the test sample is subjected to quenching heat treatment in a heat treatment furnace according to the preset temperature interval. S3. Mechanical grinding and polishing are performed on the test sample until the surface of the test sample reaches a mirror finish and no obvious scratches are observed under an optical microscope, thus obtaining the test surface of the sample. S4, the test surface of the sample is etched to obtain a test surface with clear microstructure; S5, based on the detection surface, the microstructure and chemical composition of the test sample are analyzed by scanning electron microscopy and energy dispersive spectroscopy to obtain the content of α-phase and β-phase in the titanium alloy test sample, specifically including: Using the scanning electron microscope and energy dispersive spectroscopy (EDS) attachment, the detection surface is observed by setting test parameters to obtain the microstructure morphology and chemical composition data of the test sample. The content of α-phase and β-phase in the titanium alloy test sample is analyzed. The test parameters include accelerating voltage, working distance, scanning image size, image magnification, and EDS acquisition time. Obtaining the microstructure morphology of the test sample includes: At least five fields of view should be observed at the center and half the radius of the sample to be tested, and representative fields of view should be selected to take microscopic tissue images as needed; S6. Based on the content of α and β phases, the β phase transformation temperature of titanium alloys is determined by comparing scanning electron microscopy images, specifically including: Compare the microstructure images of the test samples after different quenching heat treatment temperatures, wherein the microstructure images are secondary electron images or backscattered electron images; When the α-phase content in the microstructure decreases from 1% to 0%, for titanium alloys with a β-phase transformation temperature range not exceeding 10°C, the β-phase transformation temperature is the average of the heat treatment temperature represented by the test sample with an α-phase content of 0% and the heat treatment temperature represented by the adjacent sample with an α-phase content greater than 0%. When the α-phase content in the microstructure decreases from 1% to 0%, for titanium alloys with a β-phase transformation temperature range greater than 10°C, the β-phase transformation temperature is the average of the highest heat treatment temperature represented by the test sample with an α-phase content greater than 0% and the adjacent lower heat treatment temperature, and the result is rounded to the nearest integer. In step S6, when determining the β-phase transformation temperature of titanium alloys by comparing scanning electron microscope (SEM) images, the same magnification is selected for the SEM images of different samples.

2. The method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy according to claim 1, characterized in that, In step S1, cutting the titanium alloy sample to be tested specifically includes: The titanium alloy includes type a, Metastable and metastable A titanium alloy, wherein the material of the titanium alloy is an intermediate billet, a processed product, or a hot hydrogen-treated sample; The cutting criteria for the test sample are to avoid altering the original microstructure of the titanium alloy, and the sample surface should be polished. The test sample is a cylinder with a diameter of 10mm to 12mm and a height of 10mm, or a cuboid with a side length of 10mm to 12mm and a height of 10mm. Multiple test samples are grouped together and taken from the same processing stage of the product.

3. The method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy according to claim 1, characterized in that, In step S2, near the theoretical transformation temperature of the β phase of the titanium alloy test sample, the test sample is subjected to quenching heat treatment in a heat treatment furnace according to a preset temperature interval, specifically including: Within a set temperature range near the theoretical transformation temperature of the β phase of the titanium alloy test sample, several test temperature points were selected, and multiple test samples were sequentially subjected to quenching heat treatment in a heat treatment furnace at preset temperature intervals of 10°C.

4. The method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy according to claim 3, characterized in that, The heat treatment furnace is a box-type resistance furnace or a tube-type resistance furnace. The box-type resistance furnace has the function of loading a load thermocouple. The furnace temperature uniformity of the effective working area of ​​the box-type resistance furnace or the tube-type resistance furnace is not less than 3°C. During the quenching heat treatment, the holding time of the test sample is 20-40 minutes. The holding time is calculated from the time the effective working area of ​​the furnace reaches the set temperature. After the holding time is completed, the test sample is quickly taken out and immediately placed in a water tank for quenching. The quenching water temperature is not higher than 25°C and the quenching delay time is not more than 3 seconds. If a load thermocouple is used, the temperature displayed by the load thermocouple at the end of the holding time is taken as the actual temperature of the test sample.

5. The method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy according to claim 1, characterized in that, Step S3 involves mechanically grinding and polishing the sample until its surface reaches a mirror finish and shows no obvious scratches under an optical microscope, thus obtaining the test surface of the sample. Specifically, this includes: The standard for mechanical grinding is that at least 2 mm of oxide layer must be removed from the surface of the test sample to ensure complete removal of the oxide layer. Select sandpaper with a grit size ranging from coarse to fine for metallographic grinding of the test sample; The test sample was further polished using SiO2 polishing slurry until the surface of the test sample reached a mirror finish and no obvious scratches were observed under different magnifications of an optical microscope, thus obtaining the test surface of the sample.

6. The method for determining the β-phase transformation temperature in titanium alloys using scanning electron microscopy according to claim 1, characterized in that, In step S4, the surface of the sample to be tested is etched to obtain a test surface with a clear microstructure, specifically including: A mixed acid solution was selected as the corrosive agent, and the volume fraction of the mixed acid solution was HF:HNO3:H2O = 1:3:

7. The sample surface to be tested is immersed in the etching solution and etched for several seconds to obtain a test surface with a clear microstructure.

Images