scholarly journals Accurate electron channeling contrast analysis of a low angle sub-grain boundary

2015 ◽  
Vol 109 ◽  
pp. 76-79 ◽  
Author(s):  
H. Mansour ◽  
M.A. Crimp ◽  
N. Gey ◽  
N. Maloufi
Keyword(s):  
Grain Boundary ◽  
Electron Channeling ◽  
Contrast Analysis

Microcrack Nucleation and Crack Propagation in Equiaxed γ TiAl

2002 ◽  
Vol 753 ◽  
Author(s):  
Martin A. Crimp ◽  
Boon-Chi Ng ◽  
Benjamin A. Simkin ◽  
Thomas R. Bieler
Keyword(s):  
Ex Situ ◽  
Contrast Imaging ◽  
Active Deformation ◽  
Electron Channeling ◽  
Microcrack Initiation ◽  
Grain Orientations ◽  
Contrast Analysis ◽  
Defect Imaging

ABSTRACTTo gain a better understanding of the ductility limitations in TiAl alloys, the mechanisms involved in deformation strain transfer and/or microcrack initiation at grain boundaries have been examined in an equiaxed near-γ alloy. These studies have been carried out on both in-situ and ex-situ deformed bulk samples using scanning electron microscopy (SEM) techniques for both orientation analysis and deformation defect imaging. Selected area electron channeling patterns (SACPs) have allowed determination of grain orientations, eliminating ambiguity between the a and c axes. Deformation twins and dislocations have been imaged in the bulk samples using electron channeling contrast imaging (ECCI). A combination of ECCI contrast analysis and trace analysis based on orientations determined from SACP has allowed identification of the active deformation systems. Microcracks have been found to initiate at γ-γ boundaries as a result of an inability to adequately transfer twin strain from grain to grain. Once initiated, cracks propagate through cleavage and re-nucleation of grain boundary microcracks in front of the advancing crack. A geometric based predictive factor has been developed that accounts for microcrack initiation at γ-γ boundaries based in deformation twinning and strain accommodation by ordinary dislocations.

Analysis on Microstructure and Deformation Mechanics of X100 Linepipe Steel

2010 ◽  
Author(s):  
Yang Li ◽  
Meng Li ◽  
Lihua Qi ◽  
Lingkang Ji ◽  
Chunyong Huo ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Small Angle ◽  
Acicular Ferrite ◽  
Mechanical Tests ◽  
Tem Analysis ◽  
Steel Material ◽  
Contrast Analysis ◽  
Deformation Mechanics ◽  
Deformation Level ◽  
Linepipe Steel

In present paper, mechanical tests have been conducted on WT20.6mm×OD1016mm diameter Grade 690 linepipe. Microstructure is studied by means of OM, SEM, EBSD and TEM analysis. It is founded that the morphology of X100 steel consists mainly of fine acicular ferrite with little lath-shaped homogeneously distributed polygonal ferrite and very fine M/A constituent distributed on grain boundary, and the proportion of acicular ferrite reaches 64%. It is measured that effective grain size of steel material is 2.07μm for grains with an orientation as 15°. Contrast analysis for Kikuchi Pattern shows that the proportion of small-angle boundary is 45%, which provides X100 linepipe steel with a good performance of higher strength and toughness for large quantity of dislocation and substructure. High-density tangled and blocked dislocation in acicular ferrite lath is also observed in TEM morphology of X100 linepipe steel. Deformation mechanics will be discovered by micro-analysis on specimens deformed with different strain level as 0%, 5% and 8%. With the increment of deformation level, it is observed that substructure in effective grain and the proportion of small-angle grain boundary increases greatly, and the orientation of grain is also changed evidently. To study the deformation process of linepipe steel, an in situ tensile test is also conducted with SEM observation. It is also discovered that crack is initiated at the place of stress concentration, which is mainly close to the interface, and propagates along the length of M/A chip.

scholarly journals Study of a Σ13 SrTiO3 grain boundary : Comparison between HREM, Exit Wave Reconstruction and Z-contrast analysis

2003 ◽  
Vol 9 (S02) ◽  
pp. 934-935
Author(s):  
J. Ayache ◽  
C. Kisielowski ◽  
R. Kilaas ◽  
G. Passerieux ◽  
S. Lartigue
Keyword(s):  
Grain Boundary ◽  
Contrast Analysis ◽  
Z Contrast

scholarly journals Accurate electron channeling contrast analysis of dislocations in fine grained bulk materials

2014 ◽  
Vol 84-85 ◽  
pp. 11-14 ◽  
Author(s):  
H. Mansour ◽  
J. Guyon ◽  
M.A. Crimp ◽  
N. Gey ◽  
B. Beausir ◽  
...  
Keyword(s):  
Bulk Materials ◽  
Electron Channeling ◽  
Fine Grained ◽  
Contrast Analysis

Characterization of a Sub-Grain Boundary Using Accurate Electron Channeling Contrast Imaging

2015 ◽  
Vol 21 (S3) ◽  
pp. 601-602
Author(s):  
H. Mansour ◽  
M.A. Crimp ◽  
N. Gey ◽  
N Maloufi
Keyword(s):  
Grain Boundary ◽  
Contrast Imaging ◽  
Electron Channeling

Dependence of Intergranular Fracture on Boundary Topography and Cohesion

1973 ◽  
Vol 31 ◽  
pp. 150-151
Author(s):  
J. E. Doherty ◽  
A. F. Giamei ◽  
B. H. Kear ◽  
C. W. Steinke
Keyword(s):  
Grain Boundary ◽  
Room Temperature ◽  
Nickel Base Superalloy ◽  
Boundary Shear ◽  
Room Temperature Ductility ◽  
Solid Solution Matrix ◽  
Nickel Base ◽  
Solution Matrix ◽  
Different Levels ◽  
Base Superalloy

Recently we have been investigating a class of nickel-base superalloys which possess substantial room temperature ductility. This improvement in ductility is directly related to improvements in grain boundary strength due to increased boundary cohesion through control of detrimental impurities and improved boundary shear strength by controlled grain boundary micros true tures.For these investigations an experimental nickel-base superalloy was doped with different levels of sulphur impurity. The micros tructure after a heat treatment of 1360°C for 2 hr, 1200°C for 16 hr consists of coherent precipitates of γ’ Ni3(Al,X) in a nickel solid solution matrix.

Two Investigations into Grain Boundary Structure

1977 ◽  
Vol 35 ◽  
pp. 688-691
Author(s):  
P. Humble
Keyword(s):  
Grain Boundary ◽  
Dark Field ◽  
Boundary Structure ◽  
Boundary Dislocation ◽  
Bright Field ◽  
Intrinsic Structure ◽  
Weak Beam ◽  
Grain Boundary Structure ◽  
Independent Information ◽  
Diffraction Patterns

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.

Metallurgical Effects of Grain Boundary Ledges

1977 ◽  
Vol 35 ◽  
pp. 126-129
Author(s):  
L.E. Murr
Keyword(s):  
Grain Boundary ◽  
Quantitative Data ◽  
Mechanical Treatment ◽  
Unit Length ◽  
Physical And Mechanical Properties ◽  
Direct Observations ◽  
Transmission Electron ◽  
Properties Of Materials ◽  
Thermo Mechanical Treatment ◽  
Ledge Density

Ledges in grain boundaries can be identified by their characteristic contrast features (straight, black-white lines) distinct from those of lattice dislocations, for example1,2 [see Fig. 1(a) and (b)]. Simple contrast rules as pointed out by Murr and Venkatesh2, can be established so that ledges may be recognized with come confidence, and the number of ledges per unit length of grain boundary (referred to as the ledge density, m) measured by direct observations in the transmission electron microscope. Such measurements can then give rise to quantitative data which can be used to provide evidence for the influence of ledges on the physical and mechanical properties of materials.It has been shown that ledge density can be systematically altered in some metals by thermo-mechanical treatment3,4.

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