CN102103148B - Sample table for scanning electron microscope in-situ observation of stress corrosion cracking of metal material - Google Patents
Sample table for scanning electron microscope in-situ observation of stress corrosion cracking of metal material Download PDFInfo
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- CN102103148B CN102103148B CN201010236958.2A CN201010236958A CN102103148B CN 102103148 B CN102103148 B CN 102103148B CN 201010236958 A CN201010236958 A CN 201010236958A CN 102103148 B CN102103148 B CN 102103148B
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Abstract
The invention belongs to the field of research of environmental cracking of materials, and provides a sample table for scanning electron microscope (SEM) in-situ observation of stress corrosion cracking, which can realize the SEM in-situ observation of the stress corrosion cracking of a metal material in a liquid medium. The sample table is designed according to a spatial size of an SEM sample room; a micro tension sample can be loaded and kept in a constant displacement state in the aspect of loading the sample; and the sample table is placed in the liquid medium together with a constant displacement sample to produce the stress corrosion cracking, is taken out of the medium and is arranged in the SEM sample room, so that a continuous process of stress corrosion crack propagation can be observed and recorded. Meanwhile, the crack propagation speed and crack tip opening displacement can be accurately calculated according to a stress corrosion cracking SEM image. Through the sample table, the problem that the stress corrosion cracking of the material in the liquid medium cannot be observed by an SEM is solved, and the sample table is an effective tool for researching a stress corrosion cracking micromechanism of the material.
Description
Technical field
The invention belongs to material environment fault analysis field, is a kind of scanning electron microscope sample bench, and home position observation and the record of stress corrosion fracture occur at liquid medium for metal material.
Technical background
The fault analysis of material is the important topic of Materials, the transmission electron microscope of Materials Fracture (TEM) and scanning electron microscope (SEM) home position observation (in situ observation), can under electron microscope, directly observe the microcosmic continuous process of Materials Fracture, for fracture mechanism analysis provides microcosmic point the most direct evidence, because of but the most capable method of mechanism analysis.
The beginning of the eighties, first Kobayashir and Ohr etc. use transmission electron microscope original position stretching (TEM in situ tension) method, the fracture behaviour of research Mo, W, Cu, Al is directly observed and has been recorded dislocation motion, formation (DFZ Dislocation Free Zone), the dislocation of crack tip and instead fills in dynamic process long-pending and micro-crack extension under TEM.After this, Pestman and Hosson have studied the interaction of slip dislocation and low angle boundary in Ni3Al crystal by this method, the distortion of finding the intrinsic fault of superlattice (SISF) causes forming jog on slip dislocation line, in full accord with the result of computer simulation.Zielinski, Lii and Gerberich have studied the sharp emissary dislocations that splits of Fe-2wt.%Si crystal, and finding to split the quantity of sharp emissary dislocations and DFZ length and crack tip opening displacement has definite relation.G.wilde and researchist thereof have carried out TEM home position observation to the deformation and fracture process of the band of the palladium after fast cold and compound thereof recently, result shows that nanocrystalline tension failure presents along the hungry feature of brilliant fracture, and the distortion twin of crack tip becomes the extensions path along brilliant crackle.
The success of TEM-original position stretching method, has promoted widespread use and the development of SEM home position observation.Chang-Young Sona, Deng application SEM in-situ method, studied the fracture process of the Cu base alloy sintering alloy that contains precipitated phase particle, find crackle in noncrystal substrate forming core and expansion, split point passivation, deflection and connect bridge before particle, determine the vital role of composite particles.The fracture mechanism of the application such as XinhuaWu SEM original position stretching research TiAl alloy is observed crackle and in oxygen enrichment region, is formed in the region of 100nm left and right under SEM, has found the crisp phenomenon of oxidation system of alloy.
The home position observation of Electronic Speculum is also studied for the environmental cracking of material.Birnbaum research group carries out original position stretching in the supervoltage electron microscope with environmental chamber, studied the affect behavior of hydrogen on the dislocation motions such as Fe, Ni and fracture behaviour, found that the movement velocity that isolates dislocation and dislocation tangle under hydrogen pressure all obviously increases.Because liquid environment can not be realized in Electronic Speculum, Gu, Zhang, Chu etc. have designed permanent displacement loading bench, realize the TEM home position observation of stress corrosion fracture, observed the dynamic process that Cu alloy splits sharp emissary dislocations and dislocation motion and crack nucleation in liquid medium.
The SEM home position observation of liquid medium stress corrosion fracture there is not yet report.Due to the restriction of sample chamber vacuum environment in Electronic Speculum, in the sample chamber of Electronic Speculum, adding measurement mechanism and liquid environment is a unsurmountable difficult problem.This has directly limited the application of SEM original position stretching method.
The present invention uses for reference the achievement of previous work, designs and manufactures stress corrosion fracture SEM home position observation sample bench, can realize the SEM home position observation that stress corrosion fracture occurs material in liquid environment.
Summary of the invention
The present invention is metal stresses corrosion cracking SEM home position observation sample bench, has realized under the scanning electron microscope finite space and vacuum environment the stress corrosion fracture home position observation of metal in liquid medium.For the research of metal environment fracture mechanism provides effective tool.The scheme of technical solution problem of the present invention is as follows.
According to SEM sample chamber space structure design sample bench (the present invention) size, stress corrosion fracture sample is loaded on sample bench, can load and make sample that pre-crackle occur, measure stress value, the permanent displacement state that keeps sample, sample bench and sample one immerse in liquid corrosive medium, keep after certain hour, from liquid medium, take out sample bench and sample, put in SEM and observe, be recorded in the continuous process of Crack Extension under stress corrosion condition, by recording photograph, calculate crack growth rate and crack tip opening displacement.。
Particularly, the invention provides a kind of metal material stress corrosion fracture scanning electron microscope home position observation sample bench.Sample bench pedestal is comprised of former and later two semicylinders, by the fixing relative position of pin, in front and back cylindrical top each open the threaded hole of a Φ 4, for fixing experiment; The tapped through hole of Φ 4 is opened in this external front cylindrical front, screws in M4 screw for loading.
Stress corrosion sample is fixed on sample bench by M4 screw.Screw in the screw on the anterior pedestal of sample bench, act on rear portion pedestal, former and later two pedestals are realized relative displacement, thereby realize, fixing stress corrosion sample are loaded.The sample of loading is immersed in liquid corrosive medium stress corrosion fracture occurs together with sample bench, and interval certain hour takes out, and carries out SEM observation, records crack propagation process.
On micro-tension test machine, counter stress corrosion sample stretches, and obtains the load-displacement curves of sample.From the SEM picture of stress corrosion sample, measure displacement, according to load-displacement curves, demarcate, calculate crack tip stress field intensity factor.
Outstanding feature of the present invention and beneficial effect are 1. to realize in scanning electron microscope home position observation, the record of the stress corrosion fracture dynamic process that metal material occurs in liquid medium; 2. can accurately calculate crack tip opening displacement and the crack growth rate of stress corrosion fracture.
Accompanying drawing explanation
Fig. 1 is the present invention's (metal material stress corrosion fracture scanning electron microscope home position observation sample bench) Machine Design figure front view.
Fig. 2 is Machine Design figure vertical view of the present invention.
Fig. 3 is the present invention's photo in kind.1-screw rod in Fig. 3, pedestal before 2-, pedestal after 3-, 4-sample, 5-sample fixation screw nail, 6-pin.
Fig. 4 is that the present invention is contained in the photo in KYKY-2800 scanning electron microscope.Mark 1 indication is material object of the present invention.
Fig. 5 is used the present invention to be recorded to U75V steel in 1.0%HCl aqueous solution in embodiment 1, the SEM original position picture of stress corrosion fracture occurs.Fig. 5 (a) is the precrack pattern picture that keeps permanent displacement state; Fig. 5 (b) keeps the load pattern picture of 20 hours in 1.0%HCl aqueous solution; Fig. 5 (c) is the pattern picture keeping 40 hours; Fig. 5 (d) is the pattern picture keeping 60h hour.
Fig. 6 is used the present invention to be recorded to H62 brass at 0.5MNH in embodiment 2
4in OH aqueous solution, there is the SEM original position picture of stress corrosion fracture.Fig. 6 (a) is the precrack pattern picture that keeps permanent displacement state; Fig. 6 (b) is at 0.5MNH
4in OH aqueous solution, keep the load pattern picture of 5 minutes.
Fig. 7 is used the present invention to be recorded to 7075-T6 aged aluminum alloy in 0.5MNaCl aqueous solution in embodiment 3, the SEM original position picture of stress corrosion fracture occurs; Fig. 7 (a) is crackle 1.0h stress corrosion fracture picture in 0.5MNaCl aqueous solution.Fig. 7 (b) is the Crack Extension pattern picture after 2.0h.
Embodiment
(1) micro-tensile sample of machining experiment material;
(2) sample is loaded on home position observation sample bench, loads and make sample form micro-crack, keep permanent displacement state, place 24 hours;
(3) loading bench is put in SEM sample chamber, observed, record initial micro-crack;
(4) take out sample bench, be immersed in corrosive medium, keep certain hour; Time length is according to the differences such as character, media type and concentration, temperature of material.
(5) from solution, take out sample bench, alcohol cleans and dries up, and puts into SEM sample chamber, observes, records Crack Extension form;
(6) repeating step (4)-(5), record the continuous process of crackle under stress corrosion state.
(7) on the photo of recording, measure crack extending length, accurately determine the most advanced and sophisticated opening displacement of crack growth rate and paper.
Illustrate: 1. this embodiment is applicable to the process study of arbitrary metal material stress corrosion fracture; 2. micro-tensile sample size designs according to the intensity of sample bench size and different materials; 3. the corrosive medium of different materials and concentration can be selected according to needs.
Use the present invention to be recorded to U75V steel in 1.0%HCl aqueous solution, the SEM home position observation process of stress corrosion fracture occurs.This process is provided by 4 width SEM pictures: be respectively the precrack pattern picture that keeps permanent displacement state; In 1.0%HCl aqueous solution, keep the load pattern picture of 20 hours, can find out surface corrosion, Crack Extension; Keep the pattern picture of 40 hours, Crack Extension, Crack blunting; Keep the pattern picture of 60h hour, corrosion increases the weight of, and Crack Extension splits the front micro-crack of point and connects.Crack Extension was by 20 hours to 40 hours, and measurement crack tip opening displacement to 8.13 μ m, has increased by 3.13 μ m by 5.0 μ m.That is: 6=3.13 μ m.
Use the present invention to be recorded to H62 brass at 0.5MNH
4in OH aqueous solution, there is the SEM home position observation process of stress corrosion fracture.This process is provided by 2 width SEM pictures, respectively: keep the precrack pattern picture of permanent displacement state, crack tip forms skid wire; At 0.5MNH
4in OH aqueous solution, keep the load pattern picture of 5 minutes, can find out that a small amount of corrosion product appears in crackle both side surface.Measure crack length and extend to 130.0 μ m by 116.0 μ m of original state, increased by 14.0 μ m.Calculate crack growth rate: da/dt=14.0/5=2.8 μ m/min.
Use the present invention to be recorded to 7075-T6 aged aluminum alloy in 0.5MNaCl aqueous solution, the SEM home position observation process of stress corrosion fracture occurs.This process is provided by 2 width SEM pictures, is respectively crackle 1.0h stress corrosion fracture picture in 0.5MNaCl aqueous solution, 30 times of enlargement factors; Specimen surface corrosion, there is step crackle in crack tip; Crack Extension pattern picture after 2.0h, 200 times of enlargement factors, step Crack Extension, demonstrates the effect of precipitated phase On Crack Propagation.Step crackle front end length expands to 320.0 μ m by 179.0 μ m, has increased by 141.0 μ m.Calculate crack growth rate: da/dt=141.0/60=2.33 μ m/min.
Claims (9)
1. a metal material stress corrosion fracture scanning electron microscope home position observation sample bench, sample bench pedestal is comprised of former and later two semicylinders, by the fixing relative position of pin; The fixing sample of each threaded hole of opening a Φ 4 at the top of two semicylinders; The tapped through hole of Φ 4 is opened in this cylindrical front of external first half, screws in M4 screw and acts on rear portion pedestal, and former and later two pedestals are realized relative displacement, thereby realize, fixing stress corrosion sample are loaded; To load sample and immerse certain hour taking-up in interval in liquid medium together with sample bench, carry out SEM observation, the dynamic process of Crack Extension when observed and recorded metal material, in liquid medium, stress corrosion fracture occurs.
2. metal material stress corrosion fracture scanning electron microscope home position observation sample bench as claimed in claim 1, wherein metal material comprises iron and steel, aluminium alloy, aldary and other kinds metal material.
3. metal material stress corrosion fracture scanning electron microscope home position observation sample bench as claimed in claim 1, wherein liquid medium is alkaline aqueous solution, acidic aqueous solution, pure water.
4. metal material stress corrosion fracture scanning electron microscope home position observation sample bench as claimed in claim 1, wherein brittle fracture, ductile rupture and the tough-fragility mixed fracture of stress corrosion fracture for occurring under stress and corrosive medium double action.
5. metal material stress corrosion fracture scanning electron microscope home position observation sample bench as claimed in claim 1, wherein Crack Extension comprise that crackle is expanded continuously, the discontinuous expansion of crackle and the expansion of crackle zigzag.
6. metal material stress corrosion fracture scanning electron microscope home position observation sample bench as claimed in claim 1, wherein the enlargement factor of scanning electron microscope home position observation comprises from 20 times-20000 times continuous adjustable.
7. metal material stress corrosion fracture scanning electron microscope home position observation sample bench as claimed in claim 1, its situ dynamic process is sample fracture place from the germinating of crackle, Crack Extension, to the process of final fracture.
8. metal material stress corrosion fracture scanning electron microscope home position observation sample bench as claimed in claim 1, to sample stress application, by the screw on the anterior pedestal of precession sample bench, makes sample bench two pedestals produce relative displacement and realizes.
9. metal material stress corrosion fracture scanning electron microscope home position observation sample bench as claimed in claim 1, wherein by Crack Extension image calculation crack growth rate and crack tip opening displacement, carries out according to fracturing mechanics correlation formula.
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| CN102589950B (en) * | 2012-03-02 | 2014-05-14 | 西安石油大学 | Preparation technology of sample of scanning electron microscope for observing crack growth path |
| CN103884637B (en) * | 2012-12-21 | 2016-06-01 | 鞍钢股份有限公司 | Sample erosion profile original position microscopic examination device and method |
| CN104777046B (en) * | 2015-04-23 | 2017-05-10 | 北京航空航天大学 | Fatigue crack propagation mechanism testing method based on small time scale |
| CN105424702A (en) * | 2015-12-10 | 2016-03-23 | 东南大学 | Method for dynamically analyzing cracking failure of carbides in high speed steels |
| CN108225917B (en) * | 2018-01-18 | 2020-09-15 | 重庆大学 | Proportion-adjustable bidirectional synchronous compression experiment in-situ observation device |
| CN109781517B (en) * | 2019-01-11 | 2021-07-20 | 东南大学 | Test fixture and test method for acquiring fracture mechanical parameters of asphalt cement and aggregate interface under microscopic scale |
| CN110487628B (en) * | 2019-08-23 | 2022-04-19 | 杭州源位科技有限公司 | In-situ miniature mechanical test board |
| CN112557229B (en) * | 2020-12-08 | 2024-03-19 | 中国石油化工股份有限公司 | Method for evaluating corrosion sensitivity of metal material to slow tensile stress |
| CN113804712A (en) * | 2021-08-06 | 2021-12-17 | 云南大学 | Scanning electron microscope in-situ observation sample preparation method for lamellar carbon nitride etching process |
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| JP2000035391A (en) * | 1998-07-16 | 2000-02-02 | Seiko Instruments Inc | Method for eliminating distortion of sample in thin-piece preparation machining |
| CN1740769A (en) * | 2005-09-23 | 2006-03-01 | 东华大学 | Micro-measuring method, apparatus and use on microscope |
| CN1822305A (en) * | 2005-02-18 | 2006-08-23 | 株式会社日立科学系统 | Scanning electron microscope |
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| JPH01110204A (en) * | 1987-10-23 | 1989-04-26 | Jeol Ltd | Scanning tunnel microscope for electron microscope |
| JPH1110204A (en) * | 1997-06-19 | 1999-01-19 | Kawasaki Steel Corp | Method for preventing scale defects in hot rolled sheet |
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| JP2000035391A (en) * | 1998-07-16 | 2000-02-02 | Seiko Instruments Inc | Method for eliminating distortion of sample in thin-piece preparation machining |
| CN1822305A (en) * | 2005-02-18 | 2006-08-23 | 株式会社日立科学系统 | Scanning electron microscope |
| CN1740769A (en) * | 2005-09-23 | 2006-03-01 | 东华大学 | Micro-measuring method, apparatus and use on microscope |
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