CN117451773A - Method for measuring beta phase transition temperature in titanium alloy by adopting scanning electron microscope - Google Patents
Method for measuring beta phase transition temperature in titanium alloy by adopting scanning electron microscope Download PDFInfo
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- 229910001069 Ti alloy Inorganic materials 0.000 title claims abstract description 98
- 238000000034 method Methods 0.000 title claims abstract description 64
- 230000007704 transition Effects 0.000 title claims abstract description 53
- 238000010438 heat treatment Methods 0.000 claims abstract description 50
- 238000010791 quenching Methods 0.000 claims abstract description 26
- 230000000171 quenching effect Effects 0.000 claims abstract description 26
- 238000012360 testing method Methods 0.000 claims abstract description 20
- 238000001514 detection method Methods 0.000 claims abstract description 19
- 239000000203 mixture Substances 0.000 claims abstract description 19
- 230000009466 transformation Effects 0.000 claims abstract description 15
- 239000000126 substance Substances 0.000 claims abstract description 13
- 238000000227 grinding Methods 0.000 claims abstract description 12
- 238000005498 polishing Methods 0.000 claims abstract description 11
- 230000003287 optical effect Effects 0.000 claims abstract description 10
- 238000005520 cutting process Methods 0.000 claims abstract description 9
- 239000007788 liquid Substances 0.000 claims abstract description 5
- 238000004321 preservation Methods 0.000 claims description 12
- 238000001000 micrograph Methods 0.000 claims description 10
- 238000001228 spectrum Methods 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 6
- 230000007797 corrosion Effects 0.000 claims description 6
- 238000005260 corrosion Methods 0.000 claims description 6
- 238000012545 processing Methods 0.000 claims description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 4
- 244000137852 Petrea volubilis Species 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 239000001257 hydrogen Substances 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 4
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 3
- 230000001133 acceleration Effects 0.000 claims description 3
- 238000004626 scanning electron microscopy Methods 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 2
- 230000000007 visual effect Effects 0.000 abstract description 2
- 229910045601 alloy Inorganic materials 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- 238000004364 calculation method Methods 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 238000004455 differential thermal analysis Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 239000011651 chromium Substances 0.000 description 2
- 230000006870 function Effects 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 229910001040 Beta-titanium Inorganic materials 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 241001085205 Prenanthella exigua Species 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000008447 perception Effects 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/02—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering
- G01N25/12—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering of critical point; of other phase change
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
- G01N23/225—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion
- G01N23/2251—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion using incident electron beams, e.g. scanning electron microscopy [SEM]
Abstract
The invention discloses a method for measuring beta phase transition temperature in titanium alloy by adopting a scanning electron microscope, which comprises the following steps: cutting a sample to be tested of the titanium alloy; carrying out quenching heat treatment on the sample to be tested by using a heat treatment furnace according to a preset temperature interval near the beta-phase theoretical transformation temperature of the sample to be tested of the titanium alloy; mechanically grinding and polishing the sample to be tested until the surface reaches a mirror surface and no obvious scratch is observed under an optical microscope, so as to obtain a sample surface to be tested; corroding the surface to be detected of the sample by using a corrosive liquid to obtain a detection surface with clear microstructure; analyzing the microstructure morphology and chemical composition of the sample to be detected through a scanning electron microscope and an energy spectrometer to obtain the alpha phase and beta phase contents in the sample to be detected of the titanium alloy; and determining the beta phase transition temperature of the titanium alloy by a scanning electron microscope picture comparison method. The invention combines the advantages of a scanning electron microscope and an energy spectrometer, has the advantages of visual measurement result and high accuracy, and provides a new method for testing the beta phase transition temperature in the titanium alloy.
Description
Technical Field
The invention relates to the technical field of titanium alloy analysis and detection, in particular to a method for measuring beta phase transition temperature in titanium alloy by adopting a scanning electron microscope.
Background
The beta phase transition temperature in the titanium alloy is taken as an important parameter in the phase diagram research, is important for the heat processing and heat treatment of the titanium alloy, and is an important basis for formulating the processing technology and selecting the deformation parameters. Current methods for testing the beta phase transition temperature in titanium alloys include metallographic methods (GB/T23605-2020, HB 6623.2-1992), differential thermal analysis methods (HB 6623.1-1992), thermal expansion methods, electrical resistance methods, high temperature X-ray methods and calculation methods.
The above method has the following problems: 1) The calculation method is based on the influence of each element in the alloy on the beta phase transition temperature, the result is obtained through calculation by an empirical formula, errors of component test and the empirical formula cannot be eliminated during calculation, and the result can only be used as a reference and cannot be applied to industrial production; 2) The differential thermal analysis method, the thermal expansion method, the resistance method and the high-temperature X-ray method are all tested in the heating process of the material, and the phase change process of the titanium alloy is gradually increased along with the increase of the content of alloy elements. Therefore, the four methods can only measure the real-time phase transformation process of the titanium alloy, the lowest temperature for completely transforming the material into a beta-phase structure can not be obtained, and the data value obtained is high; the X-ray method analyzes the phase transition temperature of a material by comparing the change of the peak shape of a diffraction pattern with the change of the hydrogen content, and when the content of one phase is lower than a certain limit value (about 1% -10%, different phases are different), the existence of the phase cannot be detected. Therefore, the methods are not adopted by industrial production, only a differential thermal analysis method forms an industry standard HB 6623.1-1992, and the standard also clearly shows that the method is suitable for titanium alloys with low alloy element content (industrial pure titanium and alpha-type titanium alloys), and for titanium alloys with high alloy element content (two-phase titanium alloys and beta-titanium alloys), the standard indicates that the judgment difficulty is high; 3) The metallographic method is to observe the metallographic structure of the sample after quenching treatment at different temperatures according to preset temperature intervals by a metallographic microscope to determine the phase transition point of the titanium alloy. Therefore, the metallographic method is not affected by the length of the phase change process, can reflect the minimum temperature of all the materials converted into beta-phase structures, and is accurate and reliable. However, in actual production, although the metallographic method has corresponding standard (GB/T23605-2020) for testing the beta phase transition temperature in the titanium alloy, a metallographic microscope has limited magnification, low resolution and small depth of field (2-3 μm), and has higher requirements on the surface evenness of a sample.
Therefore, there is a need to develop a characterization solution that addresses the above-mentioned deficiencies of the prior art. Compared with a metallographic microscope, a scanning electron microscope has the advantages of wide adjustable range of magnification, high image resolution, large depth of field (a few mm), rich stereo perception of images, more abundant obtained sample information, and capability of simultaneously observing microstructure morphology and analyzing micro-area components by a matching energy spectrometer, and can accurately judge alpha phase and beta phase in the titanium alloy, thereby obtaining accurate beta phase transition temperature.
Disclosure of Invention
The invention aims to provide a method for measuring the beta-phase transition temperature in a titanium alloy by adopting a scanning electron microscope, which combines the advantages of the scanning electron microscope and an energy spectrometer to perform microscopic structure morphology observation and micro-area chemical component analysis, so that the beta-phase transition temperature in the titanium alloy can be measured more intuitively and accurately.
In order to achieve the above object, the present invention provides the following solutions:
a method for determining beta phase transition temperature in a titanium alloy using scanning electron microscopy, the method comprising the steps of:
s1, cutting a sample to be tested of titanium alloy;
s2, quenching heat treatment is carried out on the sample to be tested by using a heat treatment furnace according to a preset temperature interval near the beta-phase theoretical transformation temperature of the sample to be tested of the titanium alloy;
s3, mechanically grinding and polishing the sample to be tested until the surface of the sample to be tested reaches a mirror surface and no obvious scratch is observed under an optical microscope, so as to obtain the surface to be tested of the sample;
s4, carrying out corrosion treatment on the surface to be detected of the sample to obtain a detection surface with clear microstructure;
s5, analyzing the microstructure morphology and chemical composition of the sample to be detected through a scanning electron microscope and an energy spectrometer based on the detection surface to obtain the alpha phase and beta phase contents in the sample to be detected of the titanium alloy;
s6, based on the contents of the alpha phase and the beta phase, determining the beta phase transition temperature of the titanium alloy by a scanning electron microscope image comparison method.
Further, in the step S1, a sample to be measured of the titanium alloy is cut, which specifically includes:
the titanium alloy comprises alpha-type, alpha-beta-type and metastable beta-type titanium alloys, and the materials of the titanium alloys are intermediate blanks, processed products or heat hydrogen treatment state samples;
the cutting standard of the sample to be tested is that the original tissue of the titanium alloy is not changed, and the surface of the sample is polished;
the size of the sample to be tested is a cylinder with the diameter of 10 mm-12 mm and the height of 10mm or a cuboid with the side length of 10 mm-12 mm and the height of 10 mm;
the plurality of samples to be tested are a group and are taken from the titanium alloy of the same processing link of the product.
Further, in the step S2, a heat treatment furnace is used to perform quenching heat treatment on the to-be-measured sample according to a preset temperature interval near the β -phase theoretical transformation temperature of the to-be-measured sample of the titanium alloy, specifically including:
and selecting a plurality of test temperature points near the beta-phase theoretical transformation temperature of the to-be-tested sample of the titanium alloy, and sequentially carrying out quenching heat treatment on the plurality of to-be-tested samples at preset temperature intervals of 10 ℃ by using a heat treatment furnace.
Further, the heat treatment furnace is a box-type resistance furnace or a tubular resistance furnace, the box-type resistance furnace has the function of loading a thermocouple, and the uniformity of furnace temperature of an effective working area of the box-type resistance furnace or the tubular resistance furnace is not lower than 3 ℃;
in the quenching heat treatment process, the heat preservation time of the sample to be tested is 20-40 min, the heat preservation time is calculated from the time when the effective working area of the hearth reaches the set temperature, the sample to be tested is quickly taken out after the heat preservation is finished and immediately placed into a water tank for quenching, the quenching water temperature is not higher than 25 ℃, and the quenching delay time is not longer than 3s; if the load thermocouple is adopted, the temperature displayed by the load thermocouple at the end of heat preservation is taken as the actual temperature of the sample to be measured.
Further, the step S3 is performed with mechanical grinding and polishing treatment on the sample to be tested until the surface of the sample to be tested reaches a mirror surface and no obvious scratch is observed under an optical microscope, thereby obtaining the surface to be tested of the sample, and specifically includes:
the criteria for the mechanical grinding are: removing at least 2mm on the surface of the sample to be tested, and ensuring complete removal of the oxide layer;
selecting sand paper with granularity from coarse to fine, and carrying out metallographic grinding on a sample to be tested;
by SiO 2 The polishing solution further polishes the ground sample to be tested until the surface of the sample reaches a mirror surface, and no obvious scratches are observed under different multiples of an optical microscope, so that the surface to be tested of the sample is obtained.
Further, in the step S4, the surface to be tested of the sample is subjected to corrosion treatment to obtain a detection surface with clear microstructure, which specifically includes:
selecting a mixed acid solution as a corrosive liquid, wherein the mixed acid solution comprises HF: HNO3: h2o=1:3:7;
and (3) placing the surface to be detected of the sample into corrosive liquid, and soaking and corroding for a plurality of seconds to obtain the detection surface with clear microstructure.
Further, in the step S5, based on the detection surface, the microstructure morphology and chemical composition of the sample to be detected are analyzed by a scanning electron microscope and an energy spectrometer to obtain the α -phase and β -phase contents in the sample to be detected of the titanium alloy, which specifically includes:
and observing the detection surface by setting test parameters according to the scanning electron microscope and the energy spectrum accessory to obtain microstructure morphology and chemical composition data of the to-be-detected sample, and analyzing alpha phase and beta phase contents in the to-be-detected sample of the titanium alloy, wherein the test parameters comprise acceleration voltage, working distance, scanning image size, image magnification and energy spectrum acquisition time.
Further, the obtaining the microstructure morphology of the sample to be measured includes:
at least 5 fields of view are observed at the center and one half radius of the sample to be tested, and a representative field of view is selected according to the requirement to take a microstructure picture.
Further, the step S6 is to determine the beta phase transition temperature of the titanium alloy by a scanning electron microscope image comparison method based on the alpha phase and beta phase contents, and specifically includes:
comparing microstructure pictures of the sample to be tested after different quenching heat treatment temperatures, wherein the microstructure pictures are secondary electron pictures or back scattering electron pictures;
when the alpha phase content in the microstructure is reduced from 1% to 0%, for a titanium alloy with a beta phase transformation temperature range of not more than 10 ℃, the beta phase transformation temperature is the average value of the heat treatment temperature represented by a sample to be tested with the alpha phase content of 0% and the heat treatment temperature represented by a sample with the adjacent alpha phase content of more than 0%;
when the alpha phase content in the microstructure is reduced from 1% to 0%, for titanium alloys with beta phase transition temperatures in the range of greater than 10 ℃, the beta phase transition temperature is the average of the highest heat treatment temperature and the adjacent lower heat treatment temperature represented by the test sample with alpha phase content greater than 0%, and the result is an integer.
Further, in the step S6, when the beta-phase transition temperature of the titanium alloy is determined by the scanning electron microscope image comparison method, scanning electron microscope images of different samples are selected to have the same magnification.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects: compared with the prior art, the method for measuring the beta phase transition temperature in the titanium alloy by adopting the scanning electron microscope has the following beneficial effects:
the method comprises the steps of obtaining the microstructure morphology and chemical composition of the titanium alloy by using a scanning electron microscope and an energy spectrum accessory, judging the beta phase transition temperature of the titanium alloy by using a scanning electron microscope picture comparison method, namely, when the alpha phase content in the microstructure is reduced from 1% to 0%, taking whether the beta phase transition temperature range is larger than 10 ℃ as a judgment standard, if not, the beta phase transition temperature is the average value of the heat treatment temperature represented by a sample to be tested with the alpha phase content of 0% and the heat treatment temperature represented by a sample with the adjacent alpha phase content of more than 0%, and if so, the beta phase transition temperature is the average value of the highest heat treatment temperature represented by a sample to be tested with the alpha phase content of more than 0% and the adjacent lower heat treatment temperature, and keeping the result to be an integer;
therefore, the invention combines the advantages of a scanning electron microscope and an energy spectrometer, has the advantages of visual measurement result and high accuracy, and provides a new method for testing the beta phase transition temperature in the titanium alloy.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method of determining the beta transus temperature in a titanium alloy using scanning electron microscopy in accordance with the present invention;
FIG. 2 is a photograph of a microstructure of a TC17 original sample according to an embodiment of the present invention, wherein (a) is a secondary electron image and (b) is a back-scattered electron image;
FIG. 3 shows the microstructure composition of a TC17 original sample according to an embodiment of the present invention, wherein (a) is a back-scattered electron image, (b) is a schematic view of the alpha phase composition, and (c) is a schematic view of the beta phase composition;
FIG. 4 is a photograph of a microstructure after 890℃heat treatment according to an embodiment of the present invention, wherein (a) is a secondary electron image and (b) is a back-scattered electron image;
FIG. 5 shows the microstructure composition after 890℃heat treatment according to the embodiment of the invention, wherein (a) is a back-scattered electron image, (b) is a schematic view of the alpha phase composition, and (c) is a schematic view of the beta phase composition;
FIG. 6 is a photograph of a microstructure after heat treatment at 900 ℃ according to an embodiment of the present invention, wherein (a) is a secondary electron image and (b) is a back-scattered electron image;
fig. 7 is a photograph of a microstructure after heat treatment at 910 ℃ according to an embodiment of the present invention, wherein (a) is a secondary electron image and (b) is a back-scattered electron image.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to combine the advantages of a scanning electron microscope and an energy spectrometer to observe the microstructure morphology and analyze the micro-area components, thereby providing a new method for testing the beta phase transition temperature in the titanium alloy.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
As shown in FIG. 1, the method for measuring the beta-phase transition temperature in the titanium alloy by adopting the scanning electron microscope provided by the invention comprises the following steps of:
s1, cutting a sample to be tested of titanium alloy;
s2, quenching heat treatment is carried out on the sample to be tested by using a heat treatment furnace according to a preset temperature interval near the beta-phase theoretical transformation temperature of the sample to be tested of the titanium alloy;
s3, mechanically grinding and polishing the sample to be tested until the surface of the sample to be tested reaches a mirror surface and no obvious scratch is observed under an optical microscope, so as to obtain the surface to be tested of the sample;
s4, carrying out corrosion treatment on the surface to be detected of the sample to obtain a detection surface with clear microstructure;
s5, analyzing the microstructure morphology and chemical composition of the sample to be detected through a scanning electron microscope and an energy spectrometer based on the detection surface to obtain the alpha phase and beta phase contents in the sample to be detected of the titanium alloy;
s6, based on the contents of the alpha phase and the beta phase, determining the beta phase transition temperature of the titanium alloy by a scanning electron microscope image comparison method.
The step S1 specifically includes:
the titanium alloy comprises alpha-type, alpha-beta-type and metastable beta-type titanium alloys, and the materials of the titanium alloys are intermediate blanks, processed products or heat hydrogen treatment state samples; illustratively, intermediate billets include cast billets, forgings, slabs, and the like, and processed products include bars, plates, and the like;
the cutting standard of the sample to be tested is that the original tissue of the titanium alloy is not changed, and the surface of the sample is polished;
the size of the sample to be measured is a cylinder with the diameter of 10 mm-12 mm and the height of about 10mm or a cuboid with the side length of 10 mm-12 mm and the height of about 10 mm;
the plurality of samples to be tested are a group and are taken from the titanium alloy of the same processing link of the product.
The step S2 specifically includes:
and selecting a plurality of test temperature points (for example, 5) within a set temperature range (for example, adjacent temperatures with the same temperature difference above the transition temperature or adjacent temperatures with the same temperature difference below the transition temperature) near the beta-phase theoretical transition temperature of the to-be-tested sample of the titanium alloy, and sequentially carrying out quenching heat treatment on the plurality of to-be-tested samples at preset temperature intervals of 10 ℃ by using a heat treatment furnace. In addition, the temperature interval and the test temperature point can be appropriately increased or decreased under the early stage of ensuring the accuracy of the test result.
The heat treatment furnace is a box-type resistance furnace or a tubular resistance furnace, the box-type resistance furnace has the function of loading a thermocouple, and the uniformity of furnace temperature of an effective working area of the box-type resistance furnace or the tubular resistance furnace is not lower than 3 ℃;
in the quenching heat treatment process, the heat preservation time of the sample to be tested is 20-40 min, the heat preservation time is calculated from the time when the effective working area of the hearth reaches the set temperature, the sample to be tested is quickly taken out after the heat preservation is finished and immediately placed into a water tank for quenching, the quenching water temperature is not higher than 25 ℃, and the quenching delay time is not longer than 3s; if the load thermocouple is adopted, the temperature displayed by the load thermocouple at the end of heat preservation is taken as the actual temperature of the sample to be measured.
The step S3 specifically includes:
the criteria for the mechanical grinding are: removing at least 2mm on the surface of the sample to be tested, and ensuring complete removal of the oxide layer;
selecting sand paper with granularity from coarse to fine, and carrying out metallographic grinding on a sample to be tested;
by SiO 2 The polishing solution further polishes the ground sample to be tested until the surface of the sample reaches a mirror surface, and no obvious scratches are observed under different multiples of an optical microscope, so that the surface to be tested of the sample is obtained.
The step S4 specifically includes:
selecting a proper corrosive solution as a mixed acid solution, wherein the mixed acid solution comprises HF: HNO (HNO) 3 ：H 2 O=1:3:7; and (5) soaking and corroding for a plurality of seconds to obtain a clear detection surface of the microstructure.
In the process of obtaining the microstructure morphology and the chemical composition in the step S5, according to the scanning electron microscope and the energy spectrum accessory, the detection surface of the to-be-detected sample is observed by setting the test parameters, the microstructure morphology and the chemical composition data are obtained, and the microstructure composition (alpha phase and beta phase content) in the to-be-detected titanium alloy sample is accurately analyzed. The test parameters comprise acceleration voltage, working distance, scanning image size, image magnification and energy spectrum acquisition time.
The microstructure morphology obtained in step S5 should take into account the influence of the microscopic component fluctuations of different parts of the sample on the microstructure, at least 5 fields of view should be observed at the center and one half radius of the sample, and representative fields of view are selected as required to take a picture of the microstructure.
Step S6, based on the contents of the alpha phase and the beta phase, judges the beta phase transition temperature of the titanium alloy by a scanning electron microscope picture comparison method, and specifically comprises the following steps:
comparing microstructure pictures of the sample to be tested after different quenching heat treatment temperatures, wherein the microstructure pictures are secondary electron pictures or back scattering electron pictures;
when the alpha phase content in the microstructure is reduced from 1% to 0%, for a titanium alloy with a beta phase transformation temperature range of not more than 10 ℃, the beta phase transformation temperature is the average value of the heat treatment temperature represented by a sample to be tested with the alpha phase content of 0% and the heat treatment temperature represented by a sample with the adjacent alpha phase content of more than 0%;
when the alpha phase content in the microstructure is reduced from 1% to 0%, for titanium alloys with beta phase transition temperatures in the range of greater than 10 ℃, the beta phase transition temperature is the average of the highest heat treatment temperature and the adjacent lower heat treatment temperature represented by the test sample with alpha phase content greater than 0%, and the result is an integer.
In the step S6, when the beta-phase transition temperature of the titanium alloy is determined by the scanning electron microscope image comparison method, scanning electron microscope images of different samples are selected to have the same magnification.
Specifically, taking TC17 titanium alloy as an example, the method for measuring beta phase transition temperature in the titanium alloy by adopting a scanning electron microscope is described, and the method comprises the following steps:
s1, cutting 6 cylindrical samples to be tested, with the diameter of 10mm and the height of 10mm, from TC17 titanium alloy cast ingots by using linear cutting equipment, and polishing the surfaces of the samples to be tested;
s2, setting five heating temperature points at 880 ℃, 890 ℃, 900 ℃, 910 ℃ and 920 ℃ near the theoretical beta-phase transition temperature of the TC17 titanium alloy to-be-tested sample, respectively placing the to-be-tested sample into a tubular resistance furnace, preserving heat for 30min, and then rapidly quenching with water;
s3, selecting SiC sand paper with different mesh numbers from coarse to fine to mechanically grind the sample to be tested, and then utilizing SiO with granularity of 0.05 mu m 2 The polishing solution further polishes the sample until the surface mirror surface of the sample to be tested is polished, and no obvious scratch is observed under different multiples of an optical microscope;
s4, selecting mixed acidSolution (HF: HNO) 3 ：H 2 O=1:3:7 (volume fraction), and a clear detection surface of the microstructure is obtained after soaking and corrosion for 10 seconds;
s5, acquiring the morphology and chemical composition of a TC17 titanium alloy sample microstructure by adopting a scanning electron microscope and an energy spectrum accessory, wherein the TC17 original sample microstructure consists of an equiaxed primary alpha phase and a beta transformation structure containing a needle-shaped alpha phase (shown in figure 2), and the alpha phase is rich in Al (aluminum), the beta phase is rich in Mo (molybdenum) and Cr (chromium) as shown in figure 3, so that the alpha phase is gray and the beta phase is bright white in a back scattering electron image;
s6, observing the microstructure picture, 890 ℃ (as shown in fig. 4) and 900 ℃ (as shown in fig. 6) of the microstructure after heat treatment is composed of a primary alpha phase (gray black under the back-scattered electron image) and a beta phase, and the beta grain boundary can be observed. After heat treatment at 910 ℃, the beta grain boundaries are clearly visible, and no primary alpha phase is observed (as shown in fig. 7). Thus, the beta phase transition temperature of the sample can be determined to be 905 ℃.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (10)
1. A method for measuring beta phase transition temperature in titanium alloy by adopting a scanning electron microscope, which is characterized by comprising the following steps:
s1, cutting a sample to be tested of titanium alloy;
s2, quenching heat treatment is carried out on the sample to be tested by using a heat treatment furnace according to a preset temperature interval near the beta-phase theoretical transformation temperature of the sample to be tested of the titanium alloy;
s3, mechanically grinding and polishing the sample to be tested until the surface of the sample to be tested reaches a mirror surface and no obvious scratch is observed under an optical microscope, so as to obtain the surface to be tested of the sample;
s4, carrying out corrosion treatment on the surface to be detected of the sample to obtain a detection surface with clear microstructure;
s5, analyzing the microstructure morphology and chemical composition of the sample to be detected through a scanning electron microscope and an energy spectrometer based on the detection surface to obtain the alpha phase and beta phase contents in the sample to be detected of the titanium alloy;
s6, based on the contents of the alpha phase and the beta phase, determining the beta phase transition temperature of the titanium alloy by a scanning electron microscope image comparison method.
2. The method for determining the beta-phase transition temperature of a titanium alloy by using a scanning electron microscope according to claim 1, wherein in the step S1, a sample to be measured of the titanium alloy is cut, specifically comprising:
the titanium alloy comprises alpha-type, alpha-beta-type and metastable beta-type titanium alloys, and the materials of the titanium alloys are intermediate blanks, processed products or heat hydrogen treatment state samples;
the cutting standard of the sample to be tested is that the original tissue of the titanium alloy is not changed, and the surface of the sample is polished;
the size of the sample to be tested is a cylinder with the diameter of 10 mm-12 mm and the height of 10mm or a cuboid with the side length of 10 mm-12 mm and the height of 10 mm;
the plurality of samples to be tested are a group and are taken from the titanium alloy of the same processing link of the product.
3. The method for determining the beta-phase transition temperature of a titanium alloy by using a scanning electron microscope according to claim 1, wherein in the step S2, the sample to be tested is subjected to quenching heat treatment by using a heat treatment furnace according to a preset temperature interval around the beta-phase theoretical transition temperature of the sample to be tested of the titanium alloy, specifically comprising:
and selecting a plurality of test temperature points within a set temperature range near the beta-phase theoretical transformation temperature of the to-be-tested sample of the titanium alloy, and sequentially carrying out quenching heat treatment on the plurality of to-be-tested samples at preset temperature intervals of 10 ℃ by using a heat treatment furnace.
4. The method for measuring the beta-phase transition temperature in the titanium alloy by adopting the scanning electron microscope according to claim 3, wherein 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 thermocouple, and the furnace temperature uniformity of an effective working area of the box-type resistance furnace or the tube-type resistance furnace is not lower than 3 ℃;
in the quenching heat treatment process, the heat preservation time of the sample to be tested is 20-40 min, the heat preservation time is calculated from the time when the effective working area of the hearth reaches the set temperature, the sample to be tested is quickly taken out after the heat preservation is finished and immediately placed into a water tank for quenching, the quenching water temperature is not higher than 25 ℃, and the quenching delay time is not longer than 3s; if the load thermocouple is adopted, the temperature displayed by the load thermocouple at the end of heat preservation is taken as the actual temperature of the sample to be measured.
5. The method for determining beta-phase transition temperature in titanium alloy by using scanning electron microscope according to claim 1, wherein the step S3 comprises mechanically grinding and polishing the sample to be tested until the surface of the sample to be tested reaches a mirror surface and no obvious scratch is observed under an optical microscope, thereby obtaining the surface to be tested of the sample, and specifically comprising:
the criteria for the mechanical grinding are: removing at least 2mm on the surface of the sample to be tested, and ensuring complete removal of the oxide layer;
selecting sand paper with granularity from coarse to fine, and carrying out metallographic grinding on a sample to be tested;
by SiO 2 The polishing solution further polishes the ground sample to be tested until the surface of the sample reaches a mirror surface, and no obvious scratches are observed under different multiples of an optical microscope, so that the surface to be tested of the sample is obtained.
6. The method for determining beta-phase transition temperature in titanium alloy by scanning electron microscope according to claim 1, wherein in the step S4, the surface to be tested of the sample is subjected to corrosion treatment to obtain a detection surface with clear microstructure, specifically comprising:
selecting a mixed acid solution as a corrosive liquid, wherein the mixed acid solution comprises HF: HNO (HNO) 3 ：H 2 O＝1:3:7；
And (3) placing the surface to be detected of the sample into corrosive liquid, and soaking and corroding for a plurality of seconds to obtain the detection surface with clear microstructure.
7. The method for determining beta-phase transition temperature in a titanium alloy by using a scanning electron microscope according to claim 1, wherein in the step S5, based on the detection surface, the microstructure morphology and chemical composition of the sample to be detected are analyzed by using a scanning electron microscope and an energy spectrometer to obtain the alpha-phase and beta-phase contents in the sample to be detected of the titanium alloy, specifically comprising:
and observing the detection surface by setting test parameters according to the scanning electron microscope and the energy spectrum accessory to obtain microstructure morphology and chemical composition data of the to-be-detected sample, and analyzing alpha phase and beta phase contents in the to-be-detected sample of the titanium alloy, wherein the test parameters comprise acceleration voltage, working distance, scanning image size, image magnification and energy spectrum acquisition time.
8. The method for determining beta transus temperature in a titanium alloy by scanning electron microscopy according to claim 7, wherein the obtaining the microstructure morphology of the sample to be measured comprises:
at least 5 fields of view are observed at the center and one half radius of the sample to be tested, and a representative field of view is selected according to the requirement to take a microstructure picture.
9. The method for determining beta phase transition temperature in titanium alloy by scanning electron microscope according to claim 1, wherein the step S6 is based on the alpha phase and beta phase contents, and the beta phase transition temperature of titanium alloy is determined by scanning electron microscope picture comparison method, and specifically comprises:
comparing microstructure pictures of the sample to be tested after different quenching heat treatment temperatures, wherein the microstructure pictures are secondary electron pictures or back scattering electron pictures;
when the alpha phase content in the microstructure is reduced from 1% to 0%, for a titanium alloy with a beta phase transformation temperature range of not more than 10 ℃, the beta phase transformation temperature is the average value of the heat treatment temperature represented by a sample to be tested with the alpha phase content of 0% and the heat treatment temperature represented by a sample with the adjacent alpha phase content of more than 0%;
when the alpha phase content in the microstructure is reduced from 1% to 0%, for titanium alloys with beta phase transition temperatures in the range of greater than 10 ℃, the beta phase transition temperature is the average of the highest heat treatment temperature and the adjacent lower heat treatment temperature represented by the test sample with alpha phase content greater than 0%, and the result is an integer.
10. The method for determining beta transus temperature of titanium alloy according to claim 9, wherein in step S6, when determining beta transus temperature of titanium alloy by scanning electron microscope image comparison method, scanning electron microscope images of different samples are selected to have uniform magnification.
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