Disordering and grain boundaries of (Ni,Fe)Cr2O4 spinels from atomistic calculations

2013 ◽  
Vol 139 (13) ◽  
pp. 134702 ◽  
Author(s):  
Alain Chartier ◽  
Bogdan Golovchuk ◽  
Stéphane Gossé ◽  
Laurent Van Brutzel
Keyword(s):  
Grain Boundaries ◽  
Atomistic Calculations

scholarly journals Antagonist effects of grain boundaries between the trapping process and the fast diffusion path in nickel bicrystals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
J. Li ◽  
A. Hallil ◽  
A. Metsue ◽  
A. Oudriss ◽  
J. Bouhattate ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Hydrogen Diffusion ◽  
Short Circuit ◽  
Diffusion Path ◽  
Fast Diffusion ◽  
Fundamental Parameters ◽  
Segregation Energy ◽  
Atomistic Calculations ◽  
And Migration ◽  
Trapping Process

AbstractHydrogen-grain-boundaries interactions and their role in intergranular fracture are well accepted as one of the key features in understanding hydrogen embrittlement in a large variety of common engineer situations. These interactions implicate some fundamental processes classified as segregation, trapping and diffusion of the solute which can be studied as a function of grain boundary configuration. In the present study, we carried out an extensive analysis of four grain-boundaries based on the complementary of atomistic calculations and experimental data. We demonstrate that elastic deformation has an important contribution on the segregation energy which cannot be simply reduced to a volume change and need to consider the deviatoric part of strain. Additionally, some significant configurations of the segregation energy depend on the long-range elastic distortion and allows to rationalize the elastic contribution in three terms. By investigating the different energy barriers involved to reach all the segregation sites, the antagonist impact of grain boundaries on hydrogen diffusion and trapping process was elucidated. The segregation energy and migration energy are two fundamental parameters in order to classify the grain-boundaries as a trapping location or short circuit for diffusion.

scholarly journals Atomistic calculations of charged point defects at grain boundaries in SrTiO3

2021 ◽  
Vol 104 (5) ◽  
Author(s):  
Cong Tao ◽  
Daniel Mutter ◽  
Daniel F. Urban ◽  
Christian Elsässer
Keyword(s):  
Grain Boundaries ◽  
Point Defects ◽  
Atomistic Calculations ◽  
Charged Point

The Structure and Properties of Grain Boundaries in Ni3Al

1991 ◽  
Vol 238 ◽  
Author(s):  
M. J. Mills ◽  
S. H. Goods ◽  
S. M. Foiles
Keyword(s):  
Electron Microscopy ◽  
Grain Boundaries ◽  
Intergranular Fracture ◽  
Boron Content ◽  
Theoretical Work ◽  
Local Region ◽  
Structure And Properties ◽  
Transmission Electron ◽  
Atomistic Calculations ◽  
Compositional Disorder

ABSTRACTThe mechanical behavior of polycrystalline intermetallic compounds are often strongly influenced by the properties of the interfaces present. A classic example of this is the intergranular fracture exhibited by polycrystalline Ni3Al, and the dramatic increase in ductility upon the addition of small amounts of boron. It has been proposed that boron may promote the transmission of slip across grain boundaries by inducing the formation of a local region of compositional disorder. The results of experimental efforts to characterize the effect of boron on the structure and chemistry of these grain boundaries are summarized. Recent high resolution transmission electron microscopy studies using oriented bicrystals are described which indicate that there is no apparent change in the compositional ordering to within 0.5 nm from the boundary. These experimental results are compared with the results of atomistic calculations which have been used to examine the effect of stoichiometry and boron content on the energy and degree of ordering of these boundaries. The proposed mechanisms of intergranular fracture in Ni3Al are discussed based on this experimental and theoretical work.

scholarly journals Some Advances on Antagonist Effects of Grain Boundaries between the Trapping Process and the Fast Diffusion Path Investigated on Nickel Bicrystals

2021 ◽  
Author(s):  
xavier FEAUGAS ◽  
jiaqi Li ◽  
Malek Hallil ◽  
Arnaud Metsue ◽  
Abdelali Oudriss ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Hydrogen Diffusion ◽  
Short Circuit ◽  
Diffusion Path ◽  
Fast Diffusion ◽  
Fundamental Parameters ◽  
Segregation Energy ◽  
Atomistic Calculations ◽  
And Migration ◽  
Trapping Process

Abstract Hydrogen-grain-boundaries interactions and their role in intergranular fracture are well accepted as one of the key features in understanding hydrogen embrittlement in a large variety of common engineer situations. These interactions implicate some fundamental processes classified as segregation, trapping and diffusion of the solute which can be studied as a function of grain boundary configuration. In the present study, we carried out an extensive analysis of four grain-boundaries based on the complementary of atomistic calculations and experimental data. We demonstrate that elastic deformation has an important contribution on the segregation energy which cannot be simply reduced to a volume change and need to consider the deviatoric part of strain. Additionally, some significant configurations of the segregation energy depend on the long-range elastic distortion and allows to rationalize the elastic contribution in three terms. By investigating the different energy barriers involved to reach all the segregation sites, the antagonist impact of grain boundaries on hydrogen diffusion and trapping process was elucidated. The segregation energy and migration energy are two fundamental parameters in order to classify the grain-boundaries as a trapping location or short circuit for diffusion.

Atomic Structure Calculations of the Interaction between Lattice Dislocations and Grain Boundaries

1990 ◽  
Vol 193 ◽  
Author(s):  
B. J. Pestman ◽  
J. Th. M. De Hosson ◽  
V. Vitek ◽  
F. W. Schapink
Keyword(s):  
Grain Boundaries ◽  
Atomic Structure ◽  
Many Body ◽  
Screw Dislocations ◽  
Symmetric Tilt ◽  
Ordered Alloys ◽  
Atomistic Calculations ◽  
Tilt Boundaries ◽  
Atomic Structure Calculations ◽  
Structure Calculations

ABSTRACTThe interaction between screw dislocations and [1 1 0] symmetric tilt boundaries is investigated by atomistic calculations. In order to study the differences between fcc and ordered alloys and to study the effect of increasing ordering tendency, many-body potentials representing Cu, Cu3Au and Ni3Al were used. For the ordered alloys, the different possible ordering configurations of the boundaries that were studied are discussed.

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 176-177
Author(s):  
D. E. Fornwalt ◽  
A. R. Geary ◽  
B. H. Kear
Keyword(s):  
Electron Microscope ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Volume ◽  
Precipitate Morphology ◽  
Stress Rupture Life ◽  
Nickel Base ◽  
Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

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