scholarly journals Effect of Ni Doping on the Embrittlement of Liquid Zinc at Σ5 Fe Austenite Grain Boundary

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 27
Author(s):  
Chengfa Ding ◽  
Wangjun Peng ◽  
Zheng Ma ◽  
Yan Zhao ◽  
Huaxiang Teng ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Charge Density ◽  
Boundary Energy ◽  
Tensile Tests ◽  
Face Centered Cubic ◽  
Ni Doping ◽  
Covalent Bonds ◽  
Co Doping ◽  
Austenite Grain Boundary ◽  
Boundary Strength

In this study, first-principles computational tensile tests have been performed for the Σ5 symmetrically tilted grain boundaries of the face-centered cubic (fcc) Fe to investigate the effects of Zn and Zn-Ni doping on the boundary energy and electronic structure. The obtained results indicate that the mismatch between the sizes of Zn and Fe atoms at the Zn-doped grain boundary causes its expansion, which increases the lengths of Fe-Fe bonds, leading to their weakening, and reduces the overall boundary strength. After the Zn doping of the Fe grain boundary, Zn atoms form covalent bonds with Fe atoms, that decreases the charge density of Fe-Fe bonds and their strength. Meanwhile, the strength of the newly formed Fe-Zn covalent bonds oriented at a certain angle with respect to the grain boundary direction is very low. The breakage of Fe-Fe bonds that occurs under tensile loading rapidly decreases the boundary strength. Finally, after the Zn-Ni co-doping of the Fe grain boundary, Ni atoms form metallic bonds with Fe atoms, thus increasing both the charge density of Fe-Fe bonds (as compared with that of the Fe-Fe bonds at the Zn-doped grain boundary).

Structural Transformation of a Germanium Σ=13 (510) [001] Tilt Grain Boundary under the Electron Beam

1990 ◽  
Vol 48 (1) ◽  
pp. 52-53 ◽  
Author(s):  
Jean-Luc Rouvière ◽  
Alain Bourret
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Structural Transformation ◽  
Mirror Symmetry ◽  
High Resolution Electron Microscopy ◽  
Structural Transformations ◽  
Covalent Bonds ◽  
Resolution Electron ◽  
Tilt Grain Boundary

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

Grain boundary energy in /φ Pure Ice Bicrystals Samples

2021 ◽  
pp. 111094
Author(s):  
C.L. Di Prinzio ◽  
D. Stoler ◽  
Aguirre Varela ◽  
E. Druetta
Keyword(s):  
Grain Boundary ◽  
Boundary Energy ◽  
Grain Boundary Energy

scholarly journals Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

2021 ◽  
Author(s):  
A. Bauer ◽  
M. Vollmer ◽  
T. Niendorf
Keyword(s):  
Martensitic Transformation ◽  
Grain Boundary ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Grain Boundaries ◽  
Tensile Tests ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Grain Orientations ◽  
High Degree

AbstractIn situ tensile tests employing digital image correlation were conducted to study the martensitic transformation of oligocrystalline Fe–Mn–Al–Ni shape memory alloys in depth. The influence of different grain orientations, i.e., near-〈001〉 and near-〈101〉, as well as the influence of different grain boundary misorientations are in focus of the present work. The results reveal that the reversibility of the martensite strongly depends on the type of martensitic evolving, i.e., twinned or detwinned. Furthermore, it is shown that grain boundaries lead to stress concentrations and, thus, to formation of unfavored martensite variants. Moreover, some martensite plates seem to penetrate the grain boundaries resulting in a high degree of irreversibility in this area. However, after a stable microstructural configuration is established in direct vicinity of the grain boundary, the transformation begins inside the neighboring grains eventually leading to a sequential transformation of all grains involved.

Axisymmetric Finite-Element Analysis for Interface Migration-Controlled Shape Instabilities of Plate-Like Double-Crystal Grains

2012 ◽  
Vol 460 ◽  
pp. 230-235
Author(s):  
Pei Zhen Huang ◽  
Zhou Zhou Zhang ◽  
Jian Wei Guo ◽  
Jun Sun
Keyword(s):  
Finite Element ◽  
Grain Boundary ◽  
Chemical Potential ◽  
Boundary Energy ◽  
Element Analysis ◽  
Interface Motion ◽  
Double Crystal ◽  
Energy Principle ◽  
Chemical Potential Difference ◽  
Interface Migration

An axisymmetric finite-element method is developed to predict the evolution behavior of microstructures by interface migration. The formulation of the method is conducted on the basis of the energy principle during the interface motion. The computations extend earlier models by accounting in detail for the effects of grain-boundary energy, surface energy and chemical potential difference. The eventual shape of the plate-like double-crystal grain depends on both the initial β and the thermal grooving angle Ψ. For a given β, a critical Ψcexists. When Ψ>Ψc, the eventual shape is one made of two sphere segments with a thermal groove. When Ψ≤Ψc, grain splitting along the grain boundary occurs, and the splitting segments evolve into two spheres, respectively. Both the spheroidization time and the splitting time increase with Ψ and β increasing. The volume shrinkage rate decreases with increasing Ψ.

Dihedral angles in Cu–1wt.% Pb: Grain boundary energy and grain boundary triple line effects

2009 ◽  
Vol 57 (8) ◽  
pp. 2527-2537 ◽  
Author(s):  
D. Empl ◽  
L. Felberbaum ◽  
V. Laporte ◽  
D. Chatain ◽  
A. Mortensen
Keyword(s):  
Grain Boundary ◽  
Boundary Energy ◽  
Triple Line ◽  
Dihedral Angles ◽  
Grain Boundary Energy ◽  
Boundary Triple
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