scholarly journals Analysis of Elemental Segregation in a Microalloyed Cast Steel

2013 ◽  
Vol 652-654 ◽  
pp. 2465-2468 ◽  
Author(s):  
Jing Wei Zhao ◽  
Zheng Yi Jiang ◽  
Dong Bin Wei
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Cast Steel ◽  
Central Zone ◽  
Energy Dispersive ◽  
Surface Zone ◽  
Quantitative Investigation ◽  
X Ray ◽  
Elemental Segregation

Quantitative investigation is made on the elemental segregation in different zones of a heavy microalloyed cast steel by energy dispersive X-ray spectroscopy. It is demonstrated that C shows serious segregation tendency than that of Mn and Si, and the degree of C segregation in the surface zone is higher than that in the central zone. C enrichment is generally observed at both dendrite arm and grain boundaries, and more C segregation at dendrite arm boundary in contrast to that at grain boundary is found in this steel. The distribution of C concentration shows a decreased trend from root to tip along the dendrite arm boundary. The C concentration at trigeminal boundary intersection shows higher level than that at other position of the grain boundaries.

Impact of Energy-Dispersive Spectrometry in Materials Science Microanalysis

1998 ◽  
Vol 4 (6) ◽  
pp. 567-575 ◽  
Author(s):  
David B. Williams
Keyword(s):  
Grain Boundaries ◽  
Energy Dispersive Spectrometry ◽  
Equilibrium Phase ◽  
Boundary Segregation ◽  
Temper Embrittlement ◽  
Energy Dispersive ◽  
Small Scale ◽  
X Ray ◽  
Elemental Segregation

X-ray microanalysis of materials using energy-dispersive spectrometry (EDS) has made the greatest impact in studies of compositional changes at atomic-level interfaces. The small physical dimensions of the silicon detector make EDS the X-ray analyzer of choice for analytical transmission electron microscopy (AEM). X-ray analysis of thin foils in the AEM has contributed to our understanding of elemental segregation to interphase interfaces and grain boundaries, as well as other planar defects. Measurement of atomic diffusion on a small scale close to interphase interfaces has permitted determination of substitutional atomic diffusivities several orders of magnitude smaller than previously possible and has also led to the determination of low-temperature equilibrium phase diagrams through the measurement of local interface compositions. Elemental segregation to grain boundaries is responsible for such deleterious behavior as temper embrittlement, stress-corrosion cracking, and other forms of intergranular failure. On the other hand, segregation can bring about improvement in behavior: sintering aids in ceramics and de-embrittlement of intermetallics. EDS in the AEM has been responsible for quantitative analysis of all aspects of the segregation process and, more recently, in combination with electron energy-loss spectrometry (EELS) has given insight into why boundary segregation results in such significant macroscopic changes in properties.

X-Ray Reflectivity Study of Single- and Bicrystals of Gold

1990 ◽  
Vol 208 ◽  
Author(s):  
M. R. Fitzsimmons ◽  
E. Burkel ◽  
J. Peisl
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Diffuse Scattering ◽  
Direct Evidence ◽  
X Ray ◽  
Specular Reflectivity ◽  
Boundary Measurements

ABSTRACTX-ray reflectivity techniques have been used to characterize the surfaces of 0.4µm thick Au films epitaxially grown on single-crystals of NaCl. Measurements of both the specular and non-specular reflectivity suggest that the Au surface is very rough. The nonspecular reflectivity provides valuable information about the correlation of the heights at different points on the surface. The first in situ reflectivity study of the formation and destruction of a grain boundary shows direct evidence for the existence of diffuse scattering from the grain boundary. Measurements of several [0011 twist grain boundaries suggest that the roughness and texture of an interface depends upon the geometrical orientation of the surrounding substrates.

Improvement of polycrystalline Y–Ba–Cu–O by the addition of silver

1988 ◽  
Vol 3 (4) ◽  
pp. 605-609 ◽  
Author(s):  
G. G. Peterson ◽  
B. R. Weinberger ◽  
L. Lynds ◽  
H. A. Krasinski
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Optical Microscopy ◽  
Photoelectron Spectroscopy ◽  
Hydrocarbon Contamination ◽  
Boundary Effects ◽  
Metallic Silver ◽  
X Ray ◽  
Grain Boundary Effects ◽  
Lower Porosity

X-ray photoelectron spectroscopy, scanning Auger, and optical microscopy studies of polycrystalline superconducting pellets of Y–Ba–Cu–O/Ag are presented. Silver-laced samples have a lower porosity and a drastically reduced hydrocarbon contamination. Results indicate no detectable substitution of A g into the Y–Ba–Cu–O but a collection of metallic silver in voids and possibly along grain boundaries Intergranular silver could mitigate adverse grain boundary effects in polycrystalline Y–Ba–Cu–O.

STEM investigation of the chemistry and bonding changes associated with the grain boundary embrittlement of Cu by Bi

1996 ◽  
Vol 54 ◽  
pp. 526-527
Author(s):  
V. J. Keast ◽  
J. Bruley ◽  
D. B. Williams
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
High Current Density ◽  
High Current ◽  
Fracture Path ◽  
Scanning Electron Micrograph ◽  
Edge Structure ◽  
X Ray ◽  
Grain Boundary Embrittlement ◽  
Electron Energy Loss

It has long been known that trace amounts of Bi can embrittle Cu after appropriate heat treatments. The Bi segregates to the grain boundaries and weakens them such that failure occurs through intergranular fracture without plastic deformation. This behavior is demonstrated in the scanning electron micrograph of a typical Cu-Bi fracture surface in Figure 1. It is known that the Bi extends for only a few atomic layers into the grains on either side of the grain boundary. This narrow segregation width was been confirmed using Energy Dispersive X-ray Spectroscopy (EDS) on a VG HB603 STEM. Figure 2 shows the ratio of Bi to Cu as the probe is stepped across the grain boundary.The segregation behavior is well understood, however it is not yet properly understood how the Bi causes embrittlement once it is at the grain boundaries. The Bi must change the bonding at the boundaries so that the boundaries become weak and hence the most likely fracture path. The Electron Energy Loss Near Edge Structure (ELNES) coupled with the small probes and high current density available in a field emission STEM can provide information about the localized electronic structure and hence bonding at grain boundaries. Previous investigations indicated that the near edge structure of Cu was altered at the grain boundaries due to the presence of Bi.

Behavior of Basal Plane Dislocations and Low Angle Grain Boundary Formation in Hexagonal Silicon Carbide

2007 ◽  
Vol 556-557 ◽  
pp. 231-234 ◽  
Author(s):  
Yi Chen ◽  
Govindhan Dhanaraj ◽  
William M. Vetter ◽  
Rong Hui Ma ◽  
Michael Dudley
Keyword(s):  
Silicon Carbide ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Basal Plane ◽  
Opposite Sign ◽  
Three Dimensional ◽  
Cross Slip ◽  
X Ray ◽  
Tilt Boundaries ◽  
Edge Dislocations

The interactions between basal plane dislocations (BPDs) and threading screw and edge dislocations (TSDs and TEDs) in hexagonal SiC have been studied using synchrotron white beam x-ray topography (SWBXT). TSDs are shown to strongly interact with advancing basal plane dislocations (BPDs) while TEDs do not. A BPD can cut through an individual TED without the formation of jogs or kinks. The BPDs were observed to be pinned by TSDs creating trailing dislocation dipoles. If these dipoles are in screw orientation segments can cross-slip and annihilate also potentially leaving isolated trailing loops. The three-dimensional (3D) distribution of BPDs can lead to aggregation of opposite sign edge segments leading to the creation of low angle grain boundaries (LAGBs) characterized by pure basal plane tilt of magnitude determined by the net difference in densities of the opposite sign dislocations. Similar aggregation can also occur against pre-existing prismatic tilt boundaries made up of TED walls with the net difference in densities of the opposite sign dislocations contributing some basal plane tilt character to the LAGB.

scholarly journals Detection of Solute Segregation at Grain Boundaries

1980 ◽  
Vol 38 ◽  
pp. 360-361
Author(s):  
J. Briceno-Valero ◽  
R. Gronsky
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Solute Concentration ◽  
Boundary Region ◽  
Solute Segregation ◽  
Spectroscopic Techniques ◽  
Concentration Gradients ◽  
X Ray ◽  
Grain Boundary Plane

Studies of grain boundary segregation in metallurgical systems are traditionally based upon the premise that grain boundaries are more likely sites for solute atoms than their surrounding grains. This idea is manifested in experimnental studies which distinguish the solute concentration at boundaries from that of grain interiors using various spectroscopic techniques, including more recently, energy dispersive X-ray analysis in TEM/STEM instruments. A typical study therefore usually consists of spot or line scans across a grain boundary plane in order to detect concentration gradients at the boundary region. It has also been pointed out that there are rather severe problems in quantitatively determining the absolute solute concentration within the grain boundary, and data correction schemes for this situation have been proposed.

Microstructure and Chemistry of Grain Boundaries in Sensitized Low-Carbon High-Nitrogen Type 316 Stainless Steel

1981 ◽  
Vol 39 ◽  
pp. 288-289
Author(s):  
E. L. Hall
Keyword(s):  
Stainless Steel ◽  
Grain Boundary ◽  
Carbon Content ◽  
Grain Boundaries ◽  
Boundary Region ◽  
Nuclear Industry ◽  
Low Carbon ◽  
High Nitrogen ◽  
X Ray ◽  
316 Stainless Steel

The resistance of stainless steel to sensitization can be increased by reducing the carbon content, since sensitization is caused by the formation of chromium-rich carbides at grain boundaries which depletes the boundary region of chromium. The reduction in carbon content also lowers the strength of the steel, but this can be counteracted by adding nitrogen, leading to a series of low-carbon high-nitrogen alloys which are promising candidates for applications in the nuclear industry. However, the effect of nitrogen on the phase relationships in stainless steel are complex, and the purpose of this study is to examine these effects.Samples of 316 stainless steel with 16 w/o Cr, 9.8 w/o Ni, 2.5 w/o Mo, 0.03 w/o C, and 0.06-0.16 w/o N which had been solutionized and then aged at 600-700°C for 3-300 hours were used. Grain boundary phases were identified using electron diffraction, and grain boundary chemistry was measured using X-ray spectroscopy with a 10nm probe, either positioned directly on the boundary or stepped across the boundary with a spatial resolution of 50nm. The Cliff-Lorimer method was used to quantify the x-ray results.

Segregation of Yttrium at Grain Boundaries in α-Al2O3

2000 ◽  
Vol 654 ◽  
Author(s):  
Stefan Nufer ◽  
Wolfgang Kurtz ◽  
Manfred Rühle
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Quantitative Comparison ◽  
X Ray ◽  
Mass Absorption ◽  
Α Al2o3

AbstractQuantitative X-ray analysis allows the investigation of yttrium-doped grain boundaries. In the present study well-defined bicrystal interfaces were characterized. The quantitative comparison of segregation at different bicrystals requires a correction of artifacts in the X-ray spectra due to mass absorption, fluorescence, and beam spread. Mean grain boundary excess values of 3 Y/nm2 and around 5 Y/nm2 were found at a ∑17 and ∑37 symmetrical grain boundary, respectively. Additionally, with the ∑17 bicrystal YAG precipitation and presence of silicon was found.

Thermal and Electromigration-Induced Strains in Copper Conductor Lines: X-ray Microbeam Measurements and Analysis

2006 ◽  
Vol 914 ◽  
Author(s):  
G. Wang ◽  
H. Zhang ◽  
G. S. Cargill III ◽  
C. -K. Hu ◽  
Y. Ge ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Fiber Texture ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
Interface Diffusion ◽  
X Ray ◽  
Copper Conductor ◽  
Random Texture ◽  
Diffusion Paths ◽  
Low K

AbstractWe have carried out measurements of electromigration-induced strains in copper conductor lines using microbeam energy dispersive x-ray diffraction. Strains developed in random texture damascene Cu 2μm-wide, 0.16 μm-thick conductor lines with TaN liners in low-k dielectric during electromigration at 350°C are much smaller than electromigration-induced strains in (111) fiber texture Al-on-Si, 10μm-wide, SiO2 passivated conductor lines. The reasons for these differences in electromigration behavior may involve the different roles of grain boundary and interface diffusion paths and the different passivation structures and materials for the two types of samples.

scholarly journals Structure and Behaviour of Grain Boundaries in Polycrystalline Ice

1978 ◽  
Vol 21 (85) ◽  
pp. 589-605
Author(s):  
Akira Higashi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Moving Boundary ◽  
Boundary Energy ◽  
Coincidence Site Lattice ◽  
Geometrical Model ◽  
Grain Boundary Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Polycrystalline Ice

AbstractRecent progress in studies of the structure and behaviour of grain boundaries in ice are reviewed. As a lattice geometrical model of the boundary, the coincidence-site lattice (CSL) model is considered for ice crystals. Some evidence of the validity of this model is presented through observations of special shapes of natural snow, results of grain-boundary energy measurements, and direct microscopic observations of boundaries by X-ray diffraction topography. Although methods of measurement of grain-boundary energy have been developed recently, results are still not adequate to be analysed in terms of real energetics for comparison with models of atomic bonding. Modern methods of observing grain boundaries in ice using X-ray diffraction topography are described. Observations of migrating boundaries have revealed that faceting along most closely packed CSL points impede the migration of the CSL boundaries whilst increased numbers of steps among facets with boundaries of other kinds enhance it. The mobility of a fast-moving boundary has been determined to be of the order of 10-10 cm3 dyn-1 s-1 (10-11 m3 N-1 s-1) either in the case when the driving force is the capillary force due to the boundary energy or when it is the stored energy of dislocations.

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