scholarly journals Decorrelated Dislocation Movement in the γ-Matrix Channels of a Ni-Based Superalloy: Experiment and Dislocation Dynamics Simulation

2011 ◽  
Vol 278 ◽  
pp. 13-18
Author(s):  
Florence Pettinari-Sturmel ◽  
Joël Douin ◽  
Didier Locq ◽  
Pierre Caron ◽  
Armand Coujou
Keyword(s):  
Partial Dislocation ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Deformation Mechanisms ◽  
Narrow Channels ◽  
Microscopic Scale ◽  
Transmission Electron ◽  
Dislocation Movement ◽  
Low Strain Rate

The mechanical behavior of the polycrystalline NR3 Ni-based superalloy has been investigated at the microscopic scale. The elementary deformation mechanisms have been analyzed using transmission electron microscope observations as well as in situ straining experiments. Under low stress and relatively low strain rate conditions, a large variety of shearing micromechanisms has been observed depending on the local microstructure and the local effective stress. The influence of the smallest precipitates on the creep behavior has been enlightened: they induce narrow channels which act as obstacle for the movement of the dislocations. In the case of the narrowest channel, the deformation can operate by the propagation of Shockley dislocations or else, by the only propagation of the leading partial resulting from the partial dislocation decorrelation. The occurrence of the observed micromechanisms has been quantitatively analyzed using a nodal dislocation dynamics simulation.

scholarly journals Anti-twinning in nanoscale tungsten

2020 ◽  
Vol 6 (23) ◽  
pp. eaay2792
Author(s):  
Jiangwei Wang ◽  
Zhi Zeng ◽  
Minru Wen ◽  
Qiannan Wang ◽  
Dengke Chen ◽  
...  
Keyword(s):  
Nucleation And Growth ◽  
Shear Displacement ◽  
Atomic Scale ◽  
Deformation Mechanisms ◽  
Body Centered Cubic ◽  
Plastic Shear ◽  
Transmission Electron ◽  
20 Nm ◽  
Scale Shear

Nanomaterials often surprise us with unexpected phenomena. Here, we report a discovery of the anti-twinning deformation, previously thought impossible, in nanoscale body-centered cubic (BCC) tungsten crystals. By conducting in situ transmission electron microscopy nanomechanical testing, we observed the nucleation and growth of anti-twins in tungsten nanowires with diameters less than about 20 nm. During anti-twinning, a shear displacement of 1/3〈111〉 occurs on every successive {112} plane, in contrast to an opposite shear displacement of 1/6〈1¯1¯1¯〉 by ordinary twinning. This asymmetry in the atomic-scale shear pathway leads to a much higher resistance to anti-twinning than ordinary twinning. However, anti-twinning can become active in nanosized BCC crystals under ultrahigh stresses, due to the limited number of plastic shear carriers in small crystal volumes. Our finding of the anti-twinning phenomenon has implications for harnessing unconventional deformation mechanisms to achieve high mechanical preformation by nanomaterials.

Observation of Ag Precipitate in CuAgZr Alloy during In Situ High Temperature TEM

2017 ◽  
Vol 263 ◽  
pp. 50-54
Author(s):  
Waraporn Piyawit ◽  
Panya Buahombura
Keyword(s):  
High Temperature ◽  
Heating Process ◽  
Minor Variation ◽  
Transmission Electron ◽  
Large Lattice ◽  
Dislocation Movement ◽  
Higher Temperature ◽  
Average Size ◽  
A Minor

CuAgZr alloy is a minor variation of CuAg alloy that is remarkably known for good combination of strength and electrical conductivity. Strengthening and conductivity enhancing of CuAgZr alloy is essentially proficient by the precipitation of Ag precipitates. The behavior of Ag precipitates at high temperature was investigated using in-situ transmission electron microscopy. These nanoscale Ag precipitates are formed in CuAgZr alloy during heating process with the average size of 5 nm. Growth of precipitates at higher temperature can be explained by the consumption of solute diffusing from smaller precipitates. Dislocation looping at high temperature would be the effects of a large lattice strain along matrix/precipitate interface that would retard the dislocation movement.

scholarly journals Low-temperature plasticity of olivine revisited with in situ TEM nanomechanical testing

2016 ◽  
Vol 2 (3) ◽  
pp. e1501671 ◽  
Author(s):  
Hosni Idrissi ◽  
Caroline Bollinger ◽  
Francesca Boioli ◽  
Dominique Schryvers ◽  
Patrick Cordier
Keyword(s):  
Low Temperature ◽  
Tensile Testing ◽  
Mantle Convection ◽  
Plate Tectonics ◽  
Dislocation Dynamics ◽  
In Situ Tem ◽  
Nanomechanical Testing ◽  
Transmission Electron ◽  
Higher Temperature

The rheology of the lithospheric mantle is fundamental to understanding how mantle convection couples with plate tectonics. However, olivine rheology at lithospheric conditions is still poorly understood because experiments are difficult in this temperature range where rocks and mineral become very brittle. We combine techniques of quantitative in situ tensile testing in a transmission electron microscope and numerical modeling of dislocation dynamics to constrain the low-temperature rheology of olivine. We find that the intrinsic ductility of olivine at low temperature is significantly lower than previously reported values, which were obtained under strain-hardened conditions. Using this method, we can anchor rheological laws determined at higher temperature and can provide a better constraint on intermediate temperatures relevant for the lithosphere. More generally, we demonstrate the possibility of characterizing the mechanical properties of specimens, which can be available in the form of submillimeter-sized particles only.

In-situ transmission electron microscopy of partial-dislocation glide in 4H-SiC under electron radiation

2012 ◽  
Vol 101 (4) ◽  
pp. 042102 ◽  
Author(s):  
Yutaka Ohno ◽  
Ichiro Yonenaga ◽  
Kotaro Miyao ◽  
Koji Maeda ◽  
Hidekazu Tsuchida
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Partial Dislocation ◽  
Electron Radiation ◽  
Dislocation Glide ◽  
Transmission Electron

A study of the submicron indent-induced plastic deformation

1999 ◽  
Vol 14 (6) ◽  
pp. 2251-2258 ◽  
Author(s):  
C. F. Robertson ◽  
M. C. Fivel
Keyword(s):  
Plastic Deformation ◽  
Three Dimensional ◽  
Dislocation Nucleation ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Nanoindentation Test ◽  
Experimental Conditions ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Transmission Electron

A new method has been developed to achieve a better understanding of submicron indent-induced plastic deformation. This method combines numerical modeling and various experimental data and techniques. Three-dimensional discrete dislocation dynamics simulation and the finite element method (FEM) were used to model the experimental conditions associated with nanoindentation testing in fcc crystals. Transmission electron microscopy (TEM) observations of the indent-induced plastic volume and analysis of the experimental loading curve help in defining a complete set of dislocation nucleation rules, including the shape of the nucleated loops and the corresponding macroscopic loading. A validation of the model is performed through direct comparisons between a simulation and experiments for a nanoindentation test on a [001] copper single crystal up to 50 nm deep.

In-situ transmission electron microscopy and first-principles study of Au (100) surface dislocation dynamics

2013 ◽  
Vol 608 ◽  
pp. 154-164 ◽  
Author(s):  
B. Song ◽  
J. Jansen ◽  
F.D. Tichelaar ◽  
H.W. Zandbergen ◽  
G. Gajewski ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
First Principles ◽  
Dislocation Dynamics ◽  
First Principles Study ◽  
Transmission Electron

scholarly journals In Situ Study of Deformation Mechanisms in Sputtered Free-Standing Nanocrystalline Nickel Films

2004 ◽  
Vol 19 (4) ◽  
pp. 1029-1037 ◽  
Author(s):  
R. Mitra ◽  
A. Chiou ◽  
J.R. Weertman
Keyword(s):  
Deformation Mechanisms ◽  
Free Standing ◽  
Ample Evidence ◽  
Nickel Films ◽  
Major Mechanism ◽  
Transmission Electron ◽  
Grain Size Distributions ◽  
Bulk Nanocrystalline ◽  
Parallel Arrays

Nickel films of 1.5–10-μm thickness, produced by dc magnetron sputtering and with disperse grain size distributions peaking in the 30–60-nm range, were subject to in situ tensile straining in a transmission electron microscope. The deformation was stopped frequently, while keeping the load applied, for transmission electron microscopy observation of the internal structure. Contrast changes occurred in many of the grains between strain increments. Ample evidence was seen of dislocation activity, which appears to be the major mechanism for deformation of the samples. Dislocations were seen in grains as small as 20 nm. Parallel arrays of roughly equally spaced dislocations were observed, spaced about 5–10-nm apart. Intergranular nanovoids were found to form and grow with accompanying strain relief in neighboring grains. The results of the current study are generally consistent with previous in situ investigations and contribute to the understanding of deformation mechanisms in free-standing thin films, which may differ somewhat from those in bulk nanocrystalline materials or in films attached to a substrate.

Strain-Induced Structural Evolution and High Robustness in Single Crystalline Fivefold Twinned Cu@C Coaxial Nanowires

2014 ◽  
Vol 1033-1034 ◽  
pp. 1213-1219
Author(s):  
Yu Xin Zhao ◽  
Ying Zhang ◽  
Yan Peng Li ◽  
Zi Feng Yan
Keyword(s):  
Structural Evolution ◽  
Deformation Mechanisms ◽  
Facile Hydrothermal Method ◽  
Single Crystalline ◽  
Ultrahigh Strength ◽  
Tension Tests ◽  
Transmission Electron ◽  
Good Crystalline Quality ◽  
Mechanical Performances

Here, we developed single crystalline Cu@C nanowires with fivefold twinned structure via a facile hydrothermal method. In situ uniaxial tension tests of these NWs performed in transmission electron microscopy chamber reveal the ultrahigh strength (as much as 6.2 GPa) accompanied by favorable ductility (elongation>15%). The excellent performances benefit from nanoscale dimensions, unique penta-twinned geometry and good crystalline quality with protection of carbon shells. The study also provides direct experimental evidence for the theoretical modeling on the deformation mechanisms of metallic nanowires that have appeared in recent years. We expect that these findings can open a new window for applications in micro-or nanoelectromechanical devices where superior mechanical performances are desirable.

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