Effects of twist twin boundary and stacking fault on crack propagation of nanocrystal Al

2014 ◽  
Vol 95 ◽  
pp. 484-490 ◽  
Author(s):  
L. Gao ◽  
H.Y. Song ◽  
Y. Sun ◽  
Y.G. Zhang
Keyword(s):  
Crack Propagation ◽  
Twin Boundary ◽  
Stacking Fault

scholarly journals Modelling Electron Channeling Contrast Intensity of Stacking Fault and Twin Boundary Using Crystal Thickness Effect

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1696
Author(s):  
Hana Kriaa ◽  
Antoine Guitton ◽  
Nabila Maloufi
Keyword(s):  
Twin Boundary ◽  
Theoretical Approach ◽  
Stacking Fault ◽  
Thickness Effect ◽  
Specimen Thickness ◽  
Crystal Thickness ◽  
Contrast Imaging ◽  
Electron Channeling ◽  
Electron Intensity ◽  
Backscattered Electron

In a scanning electron microscope, the backscattered electron intensity modulations are at the origin of the contrast of like-Kikuchi bands and crystalline defects. The Electron Channeling Contrast Imaging (ECCI) technique is suited for defects characterization at a mesoscale with transmission electron microscopy-like resolution. In order to achieve a better comprehension of ECCI contrasts of twin-boundary and stacking fault, an original theoretical approach based on the dynamical diffraction theory is used. The calculated backscattered electron intensity is explicitly expressed as function of physical and practical parameters controlling the ECCI experiment. Our model allows, first, the study of the specimen thickness effect on the channeling contrast on a perfect crystal, and thus its effect on the formation of like-Kikuchi bands. Then, our theoretical approach is extended to an imperfect crystal containing a planar defect such as twin-boundary and stacking fault, clarifying the intensity oscillations observed in ECC micrographs.

Crack propagation mechanism of γ-TiAl alloy with pre-existing twin boundary

2019 ◽  
Vol 62 (9) ◽  
pp. 1605-1615 ◽  
Author(s):  
Hui Cao ◽  
ZhiYuan Rui ◽  
WenKe Chen ◽  
RuiCheng Feng ◽  
ChangFeng Yan
Keyword(s):  
Crack Propagation ◽  
Twin Boundary ◽  
Tial Alloy ◽  
Propagation Mechanism ◽  
Crack Propagation Mechanism

Twin-boundary and stacking-fault energies in Al and Pd

1991 ◽  
Vol 43 (3) ◽  
pp. 2018-2024 ◽  
Author(s):  
Jian-hua Xu ◽  
W. Lin ◽  
A. J. Freeman
Keyword(s):  
Twin Boundary ◽  
Stacking Fault ◽  
Stacking Fault Energies

Temperature Coefficient for Twin Boundary Free Energy in 304 Stainless Steel: An Electron Microscope Study

1972 ◽  
Vol 30 ◽  
pp. 652-653
Author(s):  
L.E. Murr ◽  
R.J. Horylev
Keyword(s):  
Free Energy ◽  
Temperature Coefficient ◽  
Twin Boundary ◽  
Complex Function ◽  
Pure Metal ◽  
Stacking Fault ◽  
304 Stainless Steel ◽  
Pure Metals ◽  
Interfacial Adsorption ◽  
Image Position

It has been recently shown that, as generally assumed, the coherent twin boundary free energy and the intrinsic stacking fault free energy in fee pure metals are approximately related by a factor of 2 at constant temperature, i. e.,In the case of pure metals, the temperature coefficient assumes a simple Gibbs form for a general interface (stacking fault or twin boundary):where S is the interfacial entropy per unit area of interface. It is noted in Eq. (2) that the temperature coefficient for an idealized pure metal is always negative. Thus, in the absence of interfacial adsorption of vacancies or impurities [assumed in Eq. (2)], the stacking fault and twin boundary free energies will increase with increasing temperature, and will be related by Eq. (1).In the case of multicomponent (alloy) systems, the temperature coefficient becomes a complex function of component entropy contributions, surface adsorption and desorption, and their temperature dependence:

Characteristics of Low Temperature Brittle Fracture Surface of High Nitrogen Austenitic Steel

2006 ◽  
Vol 324-325 ◽  
pp. 447-450
Author(s):  
Shi Cheng Liu ◽  
Shi Yong Liu ◽  
De Yi Liu
Keyword(s):  
Fracture Surface ◽  
Crack Propagation ◽  
Twin Boundary ◽  
Low Carbon Steel ◽  
Annealing Twin ◽  
Transgranular Fracture ◽  
Low Carbon ◽  
High Nitrogen ◽  
Boundary Fracture ◽  
Annealing Twin Boundary

Fracture surface and crack propagation in low temperature brittle fracture (LTBF) of an 18Cr-18Mn-0.7N high nitrogen austenitic steel (HNAS) were examined by means of scanning electronic microscopy, and compared with behaviours of LTBF of low carbon steel. Similar to BCC low carbon steel, the HNAS experienced a typical ductile-to-brittle transition (DBT) with decreasing temperature, and the appearance of the fracture surface transited from fibrous to granular. Dual-surface observation revealed that there were three types of fracture modes in LTBF of the HNAS: annealing twin boundary fracture, intergranular fracture, and transgranular fracture. The annealing twin boundary fracture facets were parallel to {111} planes, and were fairly flat and smooth, with a pattern of three sets of parallel straight-lines intersecting at 60. There were also bent steps that originated and terminated at grain boundaries. The transgranular fracture facets were coarse and uneven, with uniformly distributed small pits and partially river pattern on them. The intergranular fracture facets were smoothly curved ones on which more than three sets of parallel deformation structure trace lines were observed. Careful observation on crack propagation demonstrated that during LTBF of the HNAS, microcracks formed firstly at grain boundary and annealing twin boundary, and then these microcracks came together and coalesced to induce crack propagation through grains, resulting in a fracture appearance with shiny facets distributing in dull facets.

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