Quantitative transmission electron microscopy of small agglomerates in HF-O

1978 ◽  
Vol 36 (1) ◽  
pp. 336-337
Author(s):  
M. Rühle ◽  
G. Elssner ◽  
O. Ruano
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plastic Deformation ◽  
Shear Stress ◽  
Physical Properties ◽  
Temperature Dependence ◽  
Hexagonal Lattice ◽  
Transmission Electron ◽  
Critical Resolved Shear Stress

High amounts of gases or carbon are soluble on interstitial sites of the hexagonal lattice of hafnium. The gas atoms influence nearly all physical properties; e.g., the critical resolved shear stress τ (CRSS) is drastically increased with an increasing content of gas atoms. Different authors measured the temperature dependence of τ for different 0 concentrations (cO ≲ 1.5 at%). The CRSS increases strongly with decreasing measuring temperature T. Ruano and Elssner concluded intuitively from the non continious shape of the τ-T curve, that besides the interstitially solved single gas atoms also agglomerates of gas atoms should be present in the specimens. These agglomerates act as strong barriers against plastic deformation. - A superposition of the 2 types of barriers (single interstitial gas atoms and agglomerates) could explain the shape of the τ-T curve. TEM studies were performed to prove this assumption of the existence of agglomerates. Hafnium specimens with different 0 content (0.13, 0.65 and 1.17 at%0) were electrolytically thinned and investigated with a Siemens ELMISKOP 102 operated at 125 kV.

On temperature dependence of deformation mechanism and the brittle–ductile transition in semiconductors

1999 ◽  
Vol 14 (7) ◽  
pp. 2783-2793 ◽  
Author(s):  
P. Pirouz ◽  
A. V. Samant ◽  
M. H. Hong ◽  
A. Moulin ◽  
L. P. Kubin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Shear Stress ◽  
Deformation Mechanism ◽  
Low Temperatures ◽  
Partial Dislocations ◽  
Brittle Ductile Transition ◽  
Transmission Electron ◽  
Literature Evidence ◽  
Critical Resolved Shear Stress

Recent deformation experiments on semiconductors have shown the occurrence of a break in the variation of the critical resolved shear stress of the crystal as a function of temperature. These and many other examples in the literature evidence a critical temperature at which a transition occurs in the deformation mechanism of the crystal. In this paper, the occurrence of a similar transition in two polytypes of SiC is reported and correlated to the microstructure of the deformed crystals investigated by transmission electron microscopy, which shows evidence for partial dislocations carrying the deformation at high stresses and low temperatures. Based on these results and data in the literature, the explanation is generalized to other semiconductors and a possible relationship to their brittle–ductile transition is proposed.

Epitaxial Growth of NiSi2 on (011)Si

1983 ◽  
Vol 25 ◽  
Author(s):  
L.J. Chen ◽  
W.T. Lin ◽  
M.B. Chang
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Shear Stress ◽  
Epitaxial Growth ◽  
Expected Value ◽  
Edge Type ◽  
Average Spacing ◽  
Transmission Electron ◽  
Interfacial Dislocations ◽  
Critical Resolved Shear Stress

ABSTRACTEpitaxial growth of NiSi2 on (011)Si was investigated by the transmission electron microscopy. Both epitaxial and twin related NiSi2 were formed, with the former being predominant, in samples annealed at 850°C for 1/2 h. The silicides were faceted with {111} interfaces being more prominent than {100} interfaces. Interfacial dislocations were found to be of edge type with 1/6<112> Burgers vectors. The average spacing is about 700 Å which is very close to the theoretically expected value 670 Å.The absence of twins formed on (111) and (111) planes for (011) samples as well as the results obtained for (001) and (111) specimens suggest that there exists a critical resolved shear stress at the interface for the initiation of the formation of twin related NiSi2.

Nature of Slip in γ-Titanium Aluminide Above the Yield Stress Anomaly Temperature

1998 ◽  
Vol 552 ◽  
Author(s):  
S. Jiao ◽  
N. Bird ◽  
P. B. Hirsch ◽  
G. Taylor
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Shear Stress ◽  
Yield Stress ◽  
Titanium Aluminide ◽  
Transmission Electron ◽  
Different Temperatures ◽  
Critical Resolved Shear Stress

ABSTRACTCrystals of γ-TiAl, containing ∼54.5 at% Al, with various orientations were deformed at different temperatures and examined by transmission electron microscopy (TEM). It was found that while in many cases slip and climb of ordinary dislocations tend to predominate, slip by [001] dislocations can be important also. The occurrence of [001] slip has not been reported before. The values of critical resolved shear stress were determined and strong locks on [001] dislocations have been identified as local segments of ½ ⟨112] dislocations arising from interactions between [001] and ½⟨110] dislocations.

Plasticity and Microstructure of Irradiated Pd

1998 ◽  
Vol 540 ◽  
Author(s):  
N. Baluc ◽  
Y. Dai ◽  
M. Victoria
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plastic Deformation ◽  
Ambient Temperature ◽  
Tensile Deformation ◽  
Microscopic Level ◽  
Macroscopic Scale ◽  
Slip Bands ◽  
Transmission Electron ◽  
Mev Protons

AbstractSingle crystalline specimens of pure Pd have been irradiated at ambient temperature with 590 MeV protons to doses ranging between 10−4 and 10−1 dpa. Tensile deformation experiments revealed that irradiation induces hardening and embrittlement, while scanning (SEM) and transmission electron microscopy (TEM) observations showed that plastic deformation of specimens irradiated to a dose ≥ 10−2 dpa is strongly localized and yields the creation of slip bands at the macroscopic scale and of defect-free channels at the microscopic level.

Dislocations around precipitates in AlGaN epilayers

2002 ◽  
Vol 17 (8) ◽  
pp. 2007-2011 ◽  
Author(s):  
Junyong Kang ◽  
Shin Tsunekawa ◽  
Atsuo Kasuya
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Shear Stress ◽  
Dislocation Loop ◽  
Edge Dislocation ◽  
Concentration Change ◽  
Homogeneous Shear ◽  
Transmission Electron ◽  
Shape And Size ◽  
Chemical Force

Dislocations around precipitates in undoped AlGaN were investigated by transmission electron microscopy. The dislocation images were taken under different diffraction conditions. The dislocations are classified into two types, a pure edge dislocation loop and a close-;coiled helical dislocation. Both types of dislocations were found to depend on the shape and size of the precipitate sources. It is suggested that the pure edge dislocation loop results from homogeneous shear stress and the close-;coiled helical dislocation is caused by spherically symmetrical stress concentration at round ends of the precipitates and chemical force due to defect concentration change.

Hydrogen induced plastic deformation of stainless steel

1998 ◽  
Vol 513 ◽  
Author(s):  
V. J. Gadgil ◽  
E. G. Keima ◽  
H. J. M. Geijselaers
Keyword(s):  
Electron Microscopy ◽  
Finite Element Method ◽  
Transmission Electron Microscopy ◽  
Computer Simulation ◽  
Plastic Deformation ◽  
Stainless Steel ◽  
Cross Section ◽  
Dislocation Substructure ◽  
Transmission Electron ◽  
Aqueous Environments

ABSTRACTHydrogen can influence the behaviour of materials significantly. The effects of hydrogen are specially pronounced in high fugacities of hydrogen which can occur at the surface of steels in contact with certain aqueous environments. In this investigation the effect of high fugacity hydrogen on the surface of stainless steel was investigated using electrochemical cathodic charging. Microhardness was measured on the cross section. Transmission electron microscopy was used to investigate the dislocation substructure just below the surface. Computer simulation using finite element method was carried out to estimate the extent and severity of the deformation. The significance of the results are discussed in relation to the loss of ductility due to hydrogen.

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