Characterization of an anomaly in the crystallographic orientation of plate-like carbides precipitated in a wrought Ni-base superalloy

2012 ◽  
Vol 45 (4) ◽  
pp. 719-725 ◽  
Author(s):  
H. W. Jeong ◽  
I. S. Kim ◽  
S. M. Seo ◽  
Y. S. Yoo ◽  
B. G. Choi ◽  
...  
Keyword(s):  
Orientation Relationship ◽  
Crystallographic Orientation ◽  
Boundary Energy ◽  
Coincidence Site Lattice ◽  
Elastic Strain Energy ◽  
Coincidence Site Lattice Boundary ◽  
Site Lattice ◽  
Cube Orientation ◽  
The Matrix ◽  
Lattice Boundary

Face-centred cubic Cr-rich carbide is known to precipitate in a face-centred cubic matrix with a cube–cube orientation relationship, thereby minimizing the elastic strain energy. In the present study, for the first time, the precipitation was observed of an abnormal Cr-rich carbide, which did not have the cube–cube orientation relationship in its face-centred cubic matrix. The abnormally oriented carbides nucleated and grew around random grain boundaries, and were observed to have a lamellar or plate-like morphology. The crystallographic orientation anomaly was characterized by measuring the tilt angles of the three crystal poles of the matrices, carbides and adjacent grains, using a transmission electron microscope to find the closest coincidence site lattice boundary. The carbides showed a slight deviation from a cube–cube orientation with adjacent grains and did not present any particular orientational relationship with the matrix. The deviation angles from coincidence site lattice boundaries between the matrices and carbides were smaller than those between matrices and adjacent grains. The abnormally oriented carbides appeared to nucleate on adjacent grains, and underwent a rotation within the matrix during the initial stage of growth to release the phase boundary energy between the carbides and the matrix.

scholarly journals Influence of Coincidence Site Lattice Boundary on Creep Resistance of P91 Steel Weldments

2014 ◽  
Vol 86 ◽  
pp. 80-87 ◽  
Author(s):  
C.R. Das ◽  
S.K. Albert ◽  
K. Laha ◽  
J. Swaminathan ◽  
S. Ravi ◽  
...  
Keyword(s):  
Creep Resistance ◽  
Coincidence Site Lattice ◽  
Coincidence Site Lattice Boundary ◽  
P91 Steel ◽  
Site Lattice ◽  
Lattice Boundary

Characterization of Local Electrical Property of Coincidence Site Lattice Boundary in Location-controlled Silicon Islands by Scanning Probe Microscopy

2007 ◽  
Vol 1025 ◽  
Author(s):  
Nobuyuki Matsuki ◽  
R. Ishihara ◽  
A. Baiano ◽  
Y. Hiroshima ◽  
S. Inoue ◽  
...  
Keyword(s):  
Electrical Property ◽  
Coincidence Site Lattice ◽  
Coincidence Site Lattice Boundary ◽  
Site Lattice ◽  
Spreading Resistance ◽  
Transmission Electron ◽  
Lattice Boundary ◽  
Silicon Islands ◽  
Czochralski Process

AbstractLocal electrical property of coincidence site lattice boundaries (CSLBs) in location-controlled silicon islands, which are fabricated using micro-Czochralski process (grain filter), was characterized by scanning spreading resistance microscopy (SSRM) and scanning spreading resistance microscopy (SCM). Some CSLBs found in a silicon island are analyzed as Sigma 3 and Sigma 9 by electron back scattering diffraction pattern. These CSLBs are determined as {111}Sigma 3 and {221}Sigma 9 by referring to previous observation results made by transmission electron microscopy. {111}Sigma3 CSLBs shows no activity for SCM or SSRM; this is consistent with previous prediction that {111}Sigma 3 CSLB is not electrical active. We verified a capability of SCM and SSRM for characterizing local electrical property of coincidence site lattice boundary in silicon.

Dissociated Σ=27 boundaries in silicon

1988 ◽  
Vol 46 ◽  
pp. 624-625
Author(s):  
A. Garg ◽  
W.A.T. Clark ◽  
J.P. Hirth
Keyword(s):  
Electron Diffraction ◽  
Local Minimum ◽  
Boundary Energy ◽  
Coincidence Site Lattice ◽  
Boundary Plane ◽  
Low Energy ◽  
Theoretical Understanding ◽  
Site Lattice ◽  
Kikuchi Pattern ◽  
Analysis Techniques

In the last twenty years, a significant amount of work has been done in the theoretical understanding of grain boundaries. The various proposed grain boundary models suggest the existence of coincidence site lattice (CSL) boundaries at specific misorientations where a periodic structure representing a local minimum of energy exists between the two crystals. In general, the boundary energy depends not only upon the density of CSL sites but also upon the boundary plane, so that different facets of the same boundary have different energy. Here we describe TEM observations of the dissociation of a Σ=27 boundary in silicon in order to reduce its surface energy and attain a low energy configuration.The boundary was identified as near CSL Σ=27 {255} having a misorientation of (38.7±0.2)°/[011] by standard Kikuchi pattern, electron diffraction and trace analysis techniques. Although the boundary appeared planar, in the TEM it was found to be dissociated in some regions into a Σ=3 {111} and a Σ=9 {122} boundary, as shown in Fig. 1.

A symmetry-violating precipitation process induced under irradiation

1990 ◽  
Vol 48 (4) ◽  
pp. 930-931
Author(s):  
W. Kesternich
Keyword(s):  
Orientation Relationship ◽  
Neutron Irradiation ◽  
Dark Field ◽  
Fast Neutrons ◽  
Double Diffraction ◽  
Cube Orientation ◽  
Precipitate Growth ◽  
The Matrix ◽  
The Common ◽  
Diffraction Effects

TiC precipitates in austenitic steel have been found to reveal a very unusual precipitation behaviour /l,2/. As a consequence, nucleation initiated by dislocation recovery or growth induced during recrystallization can be used to create predesired modifications of the microstructure and the mechanical properties /2—3/. The extraordinary high resistance to precipitate growth and coarsening /l/ appears to be the key property in these applications and also appears to be the origin for a unique precipitate phenomenon which was observed in the present irradiation experiment.A 1.4970 type steel (15Ni—15Cr austenite, containing Ti and C) was neutron irradiated at 845 K to a dose of 2.6 x 1025 m-2 thermal neutrons (helium production) and 3.0 x 1025 fast neutrons (1.5dpa). Before irradiation the steel was solution annealed leaving about half of the Ti and C in supersaturated solution. Defect cascades introduced by the neutron irradiation acted as nucleation centres for MC (M=Ti, Nb, Mo...) precipitates as has already previously been demonstrated in Ti- and Nb-stabilized steels /4/. In addition to the common, irregularly shaped MC precipitates, however, two further precipitate variants were created during the present high temperature neutron irradiation. One precipitate variant was star—shaped with cube—on—cube orientation relationship with the matrix. The other variant was nail—shaped. Analysis of crystal structure and orientation relationship of the nail—shaped precipitates was made difficult by their small shape and by double diffraction effects. Fig. la shows a (001) SAD pattern of matrix (heavy spots) and precipitates (fine spots). The quadruplets in the vicinity of <110> are created from the new precipitates. Each of the four quadruplet spots actually consists of three closely spaced spots (Fig. lb), and the eight precipitate spots surrounding each of the matrix spots in Fig. la each consist of two spots. After the double diffraction effects had been assigned (schematic in Fig. lb for example) they were reduced by specified specimen tilting around two axes (Fig. lc). It was found by combined dark- field and diffraction analyses that all diffraction spots originated from TiC precipitates and that four orientation variants of the TiC precipitates were distinguishable. They are imaged in Fig. 1d in bright field and in Fig. 2 in four corresponding dark field images by using reflections 0 to 3 of Fig. lc. 0 shows precipitates of the common cube—on— cube orientation relationship. 1 to 3 shows nail—shaped precipitates with nail axes pointing along the three <110> directions. The diffraction analysis revealed that the lattice of the nail precipitates is rotated by 45 degrees around the nail axes from cube-on-cube orientation, thus giving rise to the three orientation variants.

Crystallography of the Mg2Y precipitates in a damping Mg–Cu–Mn–Zn–Y alloy

2016 ◽  
Vol 49 (6) ◽  
pp. 2031-2035 ◽  
Author(s):  
Xuefei Huang ◽  
Weigang Huang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Orientation Relationship ◽  
Lattice Model ◽  
Coincidence Site Lattice ◽  
Reciprocal Space ◽  
The Novel ◽  
Site Lattice ◽  
Lattice Matching ◽  
Transmission Electron

The crystallography of the Mg2Y precipitates in an Mg–Cu–Mn–Zn–Y damping alloy has been characterized by transmission electron microscopy. The novel orientation relationship between Mg2Y and the α-Mg matrix was determined as [0001]p//[0001]α, 〈10{\overline 1}0〉p//〈2{\overline 1}{\overline 1}0〉αand 〈01{\overline 1}0〉p//〈11{\overline 2}0〉α. The precipitate exhibits a polygonal morphology with four pairs of facets, each of which is normal to a Δgvector in reciprocal space. The secondary constrained coincidence site lattice model was employed to examine the preference of each facet. The results show that a much better degree of lattice matching is realized across each facet than their vicinal orientations, indicating the energetically favoured feature of the interface. The configurations of the misfit-compensating dislocations across each interface were also calculated using the O-lattice model.

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