The Effect of Pressure on Martensitic Phase Transformations

2012 ◽  
Vol 78 ◽  
pp. 13-18
Author(s):  
Vaclav Paidar ◽  
Andriy Ostapovets ◽  
Olivier Hardouin Duparc
Keyword(s):  
Martensitic Transformations ◽  
Generic Model ◽  
Many Body ◽  
Effect Of Pressure ◽  
Close Packed Structure ◽  
Bcc Structure ◽  
Packed Structure ◽  
Martensitic Phase Transformations ◽  
P Parameter ◽  
Repulsive Forces

Stability of the crystal structure is determined by the competition between attractive and repulsive interatomic forces. Using many-body exponential potentials it can be shown that the bcc structure corresponding to austenitic phases is more stable for low values of the q-parameter characterising the attractive forces for a fixed value of the p-parameter describing the repulsive forces. The structural stability can be changed with the acting pressure that may alter the martensitic transformations from the bcc-austenite to a close-packed structure. The effect of pressure is examined in a generic model employing many-body potentials and the results are compared with ab initio calculations for zirconium representing a monoatomic material with displacive phase transformation.

Phase Transformations in β- Phase Cuzn Single Crystals Induced By Ion Irradiation

2001 ◽  
Vol 7 (S2) ◽  
pp. 1254-1255
Author(s):  
Alfredo J. Tolley ◽  
Esteban A. Sanchez
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Ion Irradiation ◽  
Vibrational Entropy ◽  
Β Phase ◽  
Transmission Electron ◽  
Close Packed Structure ◽  
Bcc Structure ◽  
Packed Structure ◽  
Temperature Equilibrium

The high temperature equilibrium β phase in Cu-based alloys has a disordexed bcc structure. Its stability at high temperatures is due to the large amplitude ﹛0 ζ ζ)﹜ <0 ζ ζ> soft mode which provides a large vibrational entropy. This stability decreases with temperature as the entropy term in the Gibbs free energy becomes smaller. However, by quenching it is possible to retain the β phase avoiding decomposition by diffusion controlled transformations. in ternary β phase Cu-Zn- Al alloys, ion irradiation at room temperature has been reported to induce a phase transformation to a close packed structure or to produce γ phase precipitates. in order to further study the tendency of the β phase to decompose into other phases at room temperature, ion irradiation experiments in binary Cu-Zn single crystals were carried out using a beam of 30 keV Ar ions. The changes in the microstructure were examined using transmission electron microscopy.

Formation of Defects by Stretching Gold Nanosheet - A Simulation Study

2013 ◽  
Vol 24 ◽  
pp. 146-154 ◽  
Author(s):  
Sumali Bansal ◽  
Keya Dharamvir
Keyword(s):  
Tensile Deformation ◽  
Morphological Evolution ◽  
Face Centered Cubic ◽  
Many Body ◽  
Key Factors ◽  
Close Packed Structure ◽  
Structural Deformations ◽  
Packed Structure ◽  
Face Centered ◽  
Gupta Potential

Under tensile deformation, gold nanosheets elongate to form defects via a series of small vacancies leading to structural deformations. Behavior of finite gold nanosheets containing 57 and 73 atoms under load are investigated modeled by many-body Gupta potential. Nanosheets with close packed structure (111) plane of a face-centered-cubic structure are stretched along one of the two symmetry directions of the plane. The accessibility of these structures and their stability under load are found to be the key factors governing the morphological evolution of the gold nanosheets. It is found that major deformation is the formation of vacancies which could be called defects in the sheets and is surprisingly different from the ultimate stretching of a nanocylinder which is via neck formation. Thus this study presents completely new theoretical results for gold nanosheets.

scholarly journals Solidified Fillings of Nanopores

2005 ◽  
Vol 876 ◽  
Author(s):  
Patrick Huber ◽  
Klaus Knorr
Keyword(s):  
Pore Diameter ◽  
Stacking Faults ◽  
Pore Geometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Medium Length ◽  
Close Packed Structure ◽  
Packed Structure ◽  
Diffraction Patterns ◽  
Selection Of

AbstractWe present a selection of x-ray diffraction patterns of spherical (He, Ar), dumbbell- (N2, CO), and chain-like molecules (n-C9H20, n-C19H40) solidified in nanopores of silica glass (mean pore diameter 7nm). These patterns allow us to demonstrate how key principles governing crystallization have to be adapted in order to accomplish solidification in restricted geometries. 4He, Ar, and the spherical close packed phases of CO and N2 adjust to the pore geometry by introducing a sizeable amount of stacking faults. For the pore solidified, medium-length chainlike n-C19H40 we observe a close packed structure without lamellar ordering, whereas for the short-chain C9H20 the layering principle survives, albeit in a modified fashion compared to the bulk phase.

Two-dimensional silicon monolayers generated on c-BN(111) substrate

2015 ◽  
Vol 17 (24) ◽  
pp. 15694-15700 ◽  
Author(s):  
Haiping Wu ◽  
Yan Qian ◽  
Shaohua Lu ◽  
Erjun Kan ◽  
Ruifeng Lu ◽  
...  
Keyword(s):  
Type Structure ◽  
Two Dimensional ◽  
Compound Structure ◽  
Hexagonal Close Packed ◽  
Close Packed Structure ◽  
Hexagonal Close Packed Structure ◽  
Packed Structure ◽  
Chain Type

Three Si monolayer structures, a Si chain-type structure, a two-dimensional hexagonal close packed compound structure, and a two-dimensional hexagonal close packed structure, are generated on a c-BN(111) substrate.

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