X-ray microanalysis of grain boundary segregation in steels by s.t.e.m

1980 ◽  
Vol 295 (1413) ◽  
pp. 137-137
Keyword(s):  
Grain Boundary ◽  
Corrosion Behaviour ◽  
Boundary Segregation ◽  
Specimen Preparation ◽  
Low Alloy Steels ◽  
X Ray ◽  
Thin Foils ◽  
Scanning Transmission ◽  
Residual Elements ◽  
Alloy Steels

Equilibrium segregation of Groups IV-VI residual elements during heat treatment ( ca . 773K) of commercial low alloy steels can significantly modify their toughness, impact properties, corrosion and stress corrosion behaviour and creep life. Since these segregations are highly localized (less than about 10 nm) and do not result in microstructural changes, their direct measurement has proved difficult. The most widely used method to date is Auger electron spectroscopy (A.e.s.). This technique is surface specific, requires uncontaminated intergranularly fractured surfaces and is therefore limited by specimen preparation. The development of scanning transmission electron microscopy (s.t.e.m.) with fine electron probes, ca . 15 nm in diameter, when coupled with an energy dispersive analyser enables high resolution X-ray microanalysis within thin foils. This allows grain boundary chemical analysis for elements with atomic number not less than 12. The application of this technique has been investigated by examining segregation of residual elements in experimental iron-based alloys and commercial ferritic steels.

Quantification Of Segregation Levels Using Xeds In The Stem

1999 ◽  
Vol 5 (S2) ◽  
pp. 146-147
Author(s):  
V. J. Keast ◽  
D. B. Williams
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Scanning Transmission Electron Microscope ◽  
Factor V ◽  
X Ray ◽  
Interaction Volume ◽  
Probe Size ◽  
Scanning Transmission ◽  
The Matrix ◽  
Image Position

The quantification of grain boundary segregation levels, as measured with X-ray energy dispersive spectroscopy (XEDS) in a scanning transmission electron microscope (STEM), is dependent on the size and shape of the interaction volume. The segregation level T (in atoms/nm2) is related to the intensities of the characteristic peaks in the X-ray spectrum, Is and Im, bywhere ρ is the density of the matrix in atoms/nm3, Am and As are the atomic masses of the matrix and segregant respectively and ksm is the usual k-factor. The geometric factor, V/A, is the ratio of the volume of interaction to the area of the grain boundary inside in the interaction volume. Different models have been used to describe the interaction volume and these are illustrated in Fig. 1 and the appropriate expression for V/A is given in each case. In the simplest case, beam broadening is neglected and the interaction volume can be described as a cylinder with diameter equal to the probe size, d.

Precipitation related anomalies in kinetics of phosphorus grain boundary segregation in low alloy steels

2003 ◽  
Vol 51 (14) ◽  
pp. 4025-4032 ◽  
Author(s):  
J Janovec ◽  
A Výrostková ◽  
P Ševc ◽  
J.S Robinson ◽  
M Svoboda ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Low Alloy Steels ◽  
Alloy Steels ◽  
Kinetics Of

Microstructural aspects of phosphorus grain boundary segregation in low alloy steels

2001 ◽  
Vol 47 (1-2) ◽  
pp. 44-49 ◽  
Author(s):  
J Perháčová ◽  
D Grman ◽  
M Svoboda ◽  
J Patscheider ◽  
A Výrostková ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Low Alloy Steels ◽  
Alloy Steels

Experimental Studies of Non-Equilibrium Grain-Boundary Segregations of Phosphorus under Low Tensile Stresses

2007 ◽  
Vol 353-358 ◽  
pp. 396-399
Author(s):  
Yu Dong Fu ◽  
Gang Wang ◽  
Chen Liu ◽  
Qing Fen Li
Keyword(s):  
Grain Boundary ◽  
Experimental Studies ◽  
Boundary Segregation ◽  
Critical Time ◽  
Grain Boundary Segregation ◽  
Low Alloy Steels ◽  
Different Temperatures ◽  
Alloy Steels ◽  
The Relationship ◽  
Non Equilibrium

In the present paper, the non-equilibrium grain-boundary segregation of P atom was studied in low alloy steels subjected to a low tensile stress at different temperatures. The AES (Auger electron spectroscopy) experiments and dynamic analyses were conducted to study on the non-equilibrium grain-boundary segregation of P atom. The research results show that non-equilibrium segregation of phosphorus occurred at the grain boundaries of the steels 2.25Cr1Mo and 12Cr1MoV, while the critical time reached about 0-1 hour at constant temperatures 773 and 813K. The relationship between the diffusion rate and the diffusion time for the complex and the phosphorus atom was investigated based on the experimental results. Eventually the diffusion coefficients of complex and P were calculated with using a proposed dynamic model.

Thermodynamics of phosphorus grain boundary segregation in polycrystalline low-alloy steels

2000 ◽  
Vol 30 (1) ◽  
pp. 354-358 ◽  
Author(s):  
J. Janovec ◽  
D. Grman ◽  
J. Perh�?ov� ◽  
P. Lej?ek ◽  
J. Patscheider ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Low Alloy Steels ◽  
Alloy Steels

Effect of vanadium on grain boundary segregation of phosphorus in low alloy steels

1999 ◽  
Vol 70 (7) ◽  
pp. 269-273 ◽  
Author(s):  
Jozef Janovec ◽  
Anna Výrostková ◽  
Jana Perhácová ◽  
Viera Homolová ◽  
Hans Jürgen Grabke ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Low Alloy Steels ◽  
Alloy Steels

Studies of metaphase chromosomes in the scanning transmission x-ray microscope: Image fidelity, radiation damage and specimen preparation

1992 ◽  
Vol 50 (2) ◽  
pp. 1038-1039
Author(s):  
Shawn Williams ◽  
Xiaodong Zhang ◽  
Susan Lamm ◽  
Jack Van’t Hof
Keyword(s):  
Visible Light ◽  
Radiation Damage ◽  
Cross Section ◽  
Imaging Techniques ◽  
Dose Range ◽  
Specimen Preparation ◽  
X Rays ◽  
Metaphase Chromosomes ◽  
X Ray ◽  
Scanning Transmission

The Scanning Transmission X-ray Microscope (STXM) is well suited for investigating metaphase chromosome structure. The absorption cross-section of soft x-rays having energies between the carbon and oxygen K edges (284 - 531 eV) is 6 - 9.5 times greater for organic specimens than for water, which permits one to examine unstained, wet biological specimens with resolution superior to that attainable using visible light. The attenuation length of the x-rays is suitable for imaging micron thick specimens without sectioning. This large difference in cross-section yields good specimen contrast, so that fewer soft x-rays than electrons are required to image wet biological specimens at a given resolution. But most imaging techniques delivering better resolution than visible light produce radiation damage. Soft x-rays are known to be very effective in damaging biological specimens. The STXM is constructed to minimize specimen dose, but it is important to measure the actual damage induced as a function of dose in order to determine the dose range within which radiation damage does not compromise image quality.

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