The Effect of S Segregation on the Grain Boundary Geometry of a Σ11 Nickel Bicrystal

1991 ◽  
Vol 229 ◽  
Author(s):  
Mary C. Juhas ◽  
Louisette Priester
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Intergranular Fracture ◽  
Intergranular Corrosion ◽  
Temper Embrittlement ◽  
Solute Segregation ◽  
Premature Failure ◽  
Boundary Geometry ◽  
Engineering Materials ◽  
The Relationship

Grain boundary (GB) solute segregation has long been associated with premature failure of engineering materials. Local changes in composition at the GBs can result in such phenomena as intergranular corrosion, temper embrittlement, intergranular fracture and fatigue as well as changes in electrical properties. The relationship between GB structure and solute segregation is not well understood.

Study of Bonding of Grain Boundaries in Steels Using EELS

2005 ◽  
Vol 475-479 ◽  
pp. 4063-4066
Author(s):  
X. Zhang ◽  
Lina Zhang ◽  
Jun Jie Qi ◽  
Yue Ma
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Fracture Mode ◽  
Fracture Property ◽  
Transgranular Fracture ◽  
The Difference ◽  
Relationship Of ◽  
The Relationship

A novel EELS technique was developed to study bonding of grain boundary in many kinds of steels. We measured the normalized intensities of Fe white lines and calculated the occupancies of 3d states of iron, and then analyzed the relationship of the occupancies of 3d states of iron and the fracture property of the steels. We found that if the grain boundary has a different occupancy of 3d state of iron from that of the bulk, the steel tends to have an intergranular fracture, whereas if the grain boundary has almost the same occupancy of 3d state as the bulk, the steel tends to have a transgranular fracture. Our result shows that the difference in the occupancy of 3d state between bulk and grain boundary can be used to study the fracture mode at grain boundary in steel.

Study on the Hydrogen Effect on the Temper Embrittlement of 2.25Cr-1Mo Steel

2010 ◽  
Author(s):  
Xiliang Zhang ◽  
Changyu Zhou
Keyword(s):  
Hydrogen Embrittlement ◽  
Grain Boundary ◽  
Boundary Segregation ◽  
Temper Embrittlement ◽  
Grain Boundary Segregation ◽  
Hydrogen Effect ◽  
Electron Spectrometer ◽  
Boundary Concentration ◽  
Theory Calculation ◽  
The Relationship

The relationship between hydrogen embrittlement and temper embrittlement of 2.25Cr-1Mo steel was investigated by Auger electron spectrometer testing and electrochemical hydrogen charging. The results indicate that atomic hydrogen increases the grain boundary concentration of impurity element P and temper embrittlement. The increscent temper embrittlement degree by hydrogen will rise with further embrittlement and the relationship between increscent temper embrittlement degree and temper embrittlement degree is ΔCp = log[4.9351×(Cp)1.31687]. The grain boundary segregation theory was used and results of theory calculation and testing show that the relationship between hydrogen embrittlement and temper embrittlement can be explained by theory of grain boundary segregation. The embrittlement degree of 2.25Cr-1Mo steel which is induced by hydrogen and temper embrittlement is Cp′ = log[4.9351×(Cp)1.31687]+Cp.

Interfacial Solute Segregation Observed Using X-Ray Microanalysis in the TEM/STEM

1980 ◽  
Vol 38 ◽  
pp. 352-355
Author(s):  
D. B. Williams
Keyword(s):  
Grain Boundary ◽  
Phase Transformations ◽  
Temper Embrittlement ◽  
Solute Segregation ◽  
Image Resolution ◽  
Quantitative Microanalysis ◽  
Composition Profiles ◽  
Successful Technique ◽  
Boundary Films

Solute segregation occurring at grain boundaries or interphase interfaces can take the form of Gibbsian (equilibrium) segregation or segregation associated with phase transformations occurring at the interface. Gibbsian segregation results in monolayer level segregation and has been associated with the cause of temper embrittlement in metals and the formation of thin amorphous grain boundary films in powder-compacted ceramics. To date the most successful technique for its study has been Auger electron spectroscopy (AES) which possesses the necessary surface resolution but has the specific drawbacks of UHV operation, the need for intergranular fracture in-situ and poor image resolution. Solute segregation associated with grain boundary and interphase interface phase transformations occasionally occurs over distances > 1 μm and hence is detectable by conventional electron microprobe microanalysis. However the properties of alloys are more often than not governed by sub-micron precipitation and associated composition profiles. To date quantitative microanalysis of such phenomena has only been achieved using plasmon energy loss microanalysis(1) which unfortunately is only applicable to low Z alloys such as Al and Mg base with well defined plasmon loss spectra.

Grain Boundary Structural Transformations Induced by Solute Segregation

1984 ◽  
Vol 41 ◽  
Author(s):  
K. Sickafus ◽  
S. L. Sass
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Structural Changes ◽  
Temper Embrittlement ◽  
Analytical Techniques ◽  
Major Change ◽  
Solute Segregation ◽  
Boundary Structure ◽  
Low Alloy Steels ◽  
Fracture Surfaces

AbstractThe problem of solute segregation came to prominence with relation to studies of the temper embrittlement of low alloy steels. McLean and Northcott1(1948) first suggested that segregation of various elements to the grain boundaries was primarily responsible for the intergranular fracture observed in steels susceptible to this embrittlement. Direct evidence for segregation came much later with the development of surface sensitive analytical techniques, especially Auger electron spectroscopy (AES). Using AES, it was determined that impurity elements such as P, Sb and Sn, as well as alloying elements such as Ni and Cr, were highly concentrated at the fracture surfaces in embrittled steels2. It is not clear, however, why solute segregation changes the mechanical strength of the grain boundaries in these materials. Based on recent calculations, Messmer and Briant3 proposed that certain solute species at a grain boundary change the chemical bonding at the interface. However, other more dramatic structural rearrangements may be possible upon segregation. Such structural changes were first suggested by the observation of facetted fracture surfaces in tellurium-doped iron alloys4. In the study presented here, it is shown that low concentrations of solute can cause changes in grain boundary structure. In particular, small concentrations of Au solute were found to cause a major change in the dislocation structure of low angle [001] Fe twist boundaries. Preliminary observations on the str ucture of a Fe-0.18 at.% Au* twist boundary were presented elsewhere5. Additional results will be presented here on the effect of changes in solute concentration and misorientation angle, θ, on this structural transformation. It is believed that these observations are evidence for the occurrence of a two-dimensional phase transformation in the grain boundary, similar to that predicted by Hart6

Grain Boundary Microstructure Dependent – Intergranular Fracture in Polycrystalline Molybdenum

1999 ◽  
Vol 586 ◽  
Author(s):  
Sadahiro Tsurekawa ◽  
Tadao Watanabe
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Intergranular Fracture ◽  
Fracture Stress ◽  
Polycrystalline Materials ◽  
Grain Boundary Character Distribution ◽  
Premature Failure ◽  
Petch Relation ◽  
Practical Applications ◽  
Polycrystalline Molybdenum

ABSTRACTThe intergranular brittleness in polycrystalline materials is a source of serious problem in material processing and practical applications. To obtain a fundamental knowledge of improvement in the brittleness, we have examined the relationship between fracture behaviour and grain boundary (GB) microstructures in polycrystalline molybdenum. Quantitative analyses of GB microstructures were performed by orientation microscopy (OIM), and followed by 4-points bending tests at 77K. Thereafter, crack propagation was analyzed in connection with GB microstructures. We found the fracture stress depends on the grain size in similar manner to the Hall-Petch relation. In addition, the Hall-Petch relation also depends on the grain boundary character distribution (GBCD). The fracture stress increases with increasing the frequency of low σ GBs at constant grain size. Conversely, random GBs seem to act as weak intrinsic defects and the interconnection among them may give rise to premature failure. Therefore, the connectivity of random GBs probably becomes important as well as the GBCD to suppress the intergranular fracture.

Morphology and atomic structure of segregated grain boundaries in Cu-Sb

1992 ◽  
Vol 50 (1) ◽  
pp. 254-255
Author(s):  
R. W. Fonda ◽  
D. E. Luzzi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Atomic Structure ◽  
Copper Alloys ◽  
Polycrystalline Materials ◽  
Grain Boundary Embrittlement ◽  
Boundary Embrittlement

The properties of polycrystalline materials are strongly dependant upon the strength of internal boundaries. Segregation of solute to the grain boundaries can adversely affect this strength. In copper alloys, segregation of either bismuth or antimony to the grain boundary will embrittle the alloy by facilitating intergranular fracture. Very small quantities of bismuth in copper have long been known to cause severe grain boundary embrittlement of the alloy. The effect of antimony is much less pronounced and is observed primarily at lower temperatures. Even though moderate amounts of antimony are fully soluble in copper, concentrations down to 0.14% can cause grain boundary embrittlement.

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